Polypeptide Of Apparent Molecular Weight Research Articles

Induction of mercury‐binding peptide in whole cells and anucleated cells of Acetabularia calyculus

The present study reports the isolation and partial purification of a mercury‐binding polypeptide in whole and anucleated cells of Acetabularia calyculus. Sephadex G‐75 Gel filtration showed that cells exposed to Hg exhibit a major peak of protein(s) concomitant with both, a major peak of Hg (revealed by atomic absorption spectroscopy), and the major peak of mercury‐thiolate complex (based on a high 254 nm absorbance) accompanied by high content of SH groups. SDS‐Page electrophoresis showed that this peak contains one major polypeptide of apparent molecular weight 27.000 dalton. These results are in agreement with our previous finding of unusually high bioconcentration factor of Hg in Acetabularia related to the induction of a polypeptide in both, whole and anucleated cells of Acetabularia, in presence of Hg.

Characterization of anther‐expressed genes encoding a major class of extracellular oleosin‐like proteins in the pollen coat of Brassicaceae†

A large, heterogeneous, highly expressed gene family encoding oleosin-like proteins is described in the Brassicaceae. Seven related cDNA sequences were isolated from Brassica napus anther mRNA using RACE-PCR and compared with other recently described anther-specific oleosin-like genes from B. napus. The expression patterns of four representative members of this diverse gene family were analyzed by Northern blotting and in situ hybridization. In all cases, the genes were expressed specifically in the tapetum of 3-5 mm B. napus buds, which contained microspores at the late-vacuolate and bicellular stages of development. The predicted protein products are ordered into subclasses, each of which has a characteristic C-terminal domain, containing different amino acid motifs or repeated residues. Tryphine (pollen coat) fractions from mature B. napus pollen were found to be particularly enriched in polypeptides of apparent molecular weights 32-38 kDa, plus numerous less abundant polypeptides of less than 15 kDa. The N-terminal 15-20 residues of three of these polypeptides (12, 32 and 38 kDa) were found by microsequencing to be identical to parts of the predicted amino acid sequences of three of the tapetal-expressed oleosin-like genes. This indicates the possibility of post-translational modification of these proteins resulting in a cleavage of the primary translation products in order to generate the mature tryphine polypeptides. These data imply that a large and diverse group of oleosin-like proteins is synthesized in the tapetum of B. napus anthers and that following tapetal degradation, these proteins, possibly in modified form, then relocate to the developing microspores where they eventually constitute some of the major components of the extracellular tryphine of mature pollen grains. These proteins share a conserved 70 amino acid residue hydrophobic domain and are related structurally to the seed-specific intracellular oleosins, although their biological function may be different.

Existence of a putative specific postsynaptic density protein produced during Purkinje cell spine maturation

This study identified a 140 kDa polypeptide as a putative specific component of Purkinje cell spines' postsynaptic densities and which began to appear during the critical period of cerebellar cortex synaptogenesis. Mouse cerebellar cortices at postnatal days 5, 7, 9, 11, 15 and young adult, between days 30 and 40, were used to purify subcellular fractions of synaptosomes, synaptic membranes and postsynaptic densities. The purity of the subcellular fractions was assessed by electron microscopy and the protein composition of the different fractions was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Polypeptides of apparent molecular weights of 25, 26, 27, 30, 33, 37, 43, 45, 52, 64, 74, 85, 94, 110, 125, 130, 165 and 174 kDa were found in the synaptosomal fractions of all the ages studied, even before the critical period of synaptogenesis, at postnatal day 7, when the postsynaptic densities were still nonexistent, indicating that the polypeptides are nonspecific constituents of these structures. On the other hand, a 140 kDa polypeptide was detected in the postsynaptic density fractions at postnatal day 11, immediately after postsynaptic structures began to appear, suggesting the possibility that this protein is a specific component of the cerebellar cortex postsynaptic densities. The 140 kDa polypeptide was electroeluted from the gel and analysed for its amino acid composition by reverse-phase high-pressure liquid chromatography. The analysis showed that this protein has a high content of nonpolar amino acid residues, such as leucine, isoleucine, glycine, phenylalanine and valine. A hypothetical model relative to the participation of the 140 kDa protein in the molecular organization of the postsynaptic density is suggested which may contribute to the understanding of the role played by this structure in synaptic function.

Nucleoside diphosphate kinase from pea chloroplasts: purification, cDNA cloning and import into chloroplasts

Nucleoside diphosphate kinase (NDPK; EC 2.7.4.6) was enriched 1900-fold from purified pea (Pisum sativum L. cv. Golf.) chloroplasts. The active enzyme preparation contained two polypeptides of apparent molecular weight 18.5 kDa and 17.4 kDa. Both proteins were enzymatically active and were recognized by an antiserum raised against NDPK from spinach chloroplasts, suggesting the existence of two isoforms in pea chloroplasts. The N-terminal protein sequence data were obtained for both polypeptides and compared with the nucleotide sequence of a cDNA clone isolated from a pea cDNA library. The analysis revealed that the two NDPK forms are encoded for by one mRNA, indicating that the lower-molecular-weight form could represent a proteolytic breakdown product of the 18.5-kDa NDPK. The pea chloroplastic NDPK is made as a larger precursor protein which is imported into chloroplasts. The NDPK precursor is then processed by the stromal processing peptidase to yield the 18.5-kDa form.

A cell surface antigen expressed by astrocytes and their precursors

Increasing evidence suggests that astrocytes of the mammalian CNS are a heterogeneous population of cells that express a number of common characteristics. In most cases, astrocytes or their precursors contain a class of intermediate filaments, composed in large part of glial fibrillary acidic protein (GFAP). While the expression of GFAP immunoreactivity is a specific characteristic of astrocytes in the vertebrate CNS, not all astrocytes contain detectable levels of glial filaments, particularly during early development. We have isolated a monoclonal antibody termed 7B11 which binds to the surface of astrocytes and glial precursors, but not to other major types of neural cells. The 7B11 antigen is expressed by astrocytes in the adult CNS in vivo and in cultures of developing CNS tissue, but not on cells of the peripheral nervous system. During early development, 7B11 immunoreactivity appears prior to the expression of GFAP and is retained as punctate staining on the surface of most classes of astrocytes. During CNS maturation, however, 7B11 immunoreactivity is lost from the surface of Bergmann glia in the cerebellum, suggesting that differentiative events lead to functionally and antigenically distinct classes of CNS glial cells. In the adult spinal cord, biochemical analysis suggests that the epitope recognized by 7B11 is associated with a group of polypeptides of apparent molecular weights 200-160, 140, and 92 kD. The cellular distribution of 7B11 expression suggests that astrocytes and their precursors share a distinct cell surface antigenic property and that the expression of 7B11 immunoreactivity may be a useful operational marker for astrocytes in the absence of detectable GFAP expression.

The purification of a human mismatch-binding protein and identification of its associated ATPase and helicase activities.

A mismatch-binding protein has been purified an estimated 4500-fold from HeLa nuclear extracts using four different chromatographic steps. Two polypeptides of apparent molecular weight of 160,000 and 100,000 were present in the final affinity-purified fraction as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Partial proteolytic clipping of the protein-DNA complexes visualized after UV treatment indicated that the 100-kDa polypeptide is most likely a degradation product of the 160-kDa polypeptide. UV cross-linking experiments have shown that both these polypeptides bind specifically to oligonucleotide duplexes containing G/T mismatches. Direct DNA binding studies and band-shift competition assays showed that although the mismatch-binding protein binds with highest affinity to oligonucleotides containing G/T mismatches, it is also capable of binding to oligonucleotides containing other mispairs. The purified protein has an associated Mg(2+)-dependent ATPase activity, which is markedly enhanced in the presence of single-stranded DNA. A helicase capable of unwinding a 34-mer oligonucleotide, annealed to a complementary sequence in single-stranded M13, also copurified with the mismatch-binding protein. This reaction occurs in an ATP- and magnesium-dependent manner.

Ontogeny of cytosolic proteins capable of modulating sarcoplasmic reticulum calcium transport in heart muscle

In a previous study we described the inhibitory action of a cytosolic protein fraction from heart muscle on ATP-dependent Ca2+ uptake by sarcoplasmic reticulum (SR); further, this inhibition was shown to be blocked by an inhibitor antagonist, also derived from the cytosol (Narayanan et al. Biochim Biophys Acta 735: 53-66, 1983). The present study investigated the ontogenetic expression of the activities of Ca2+ transport inhibitor and inhibitor antagonist in heart cytosol during fetal and postnatal development of the rat. The SR Ca2+ transport inhibitor activity was undetectable in the cytosol of fetal (15- or 20-days gestation) rat heart but was manifested in the cytosol as early as one day after birth and increased progressively thereafter to reach almost adult levels within the first two weeks of postnatal development. The activity of the SR Ca2+ transport inhibitor antagonist was barely detectable in the near-term (20 days gestation) fetus but increased substantially during early postnatal development, in parallel with the rise in activity of the inhibitor. The ontogenetic appearance and increase in the activities of the Ca2+ transport inhibitor and its antagonist correlated well with the concurrent appearance and increase in the amounts of two polypeptides of apparent molecular weights 43 kDa and 64 kDa, which we have tentatively identified as the inhibitor and inhibitor antagonist, respectively. The co-ordinated expression of both the inhibitor and inhibitor antagonist activities in the cytosol during the early postnatal period parallels the morphogenesis and functional maturation of SR in cardiac muscle suggesting likely involvement of these cytosolic proteins in the physiological regulation of SR function.

Altered protein phosphorylation in murine muscular dystrophy

Protein phosphorylation has been studied in the dydy murine muscular dystrophy, both in intact muscle cells and in various membrane fractions derived from them. The results obtained showed that several polypeptides were more heavily phosphorylated in dystrophic myotubes in culture as well as in dystrophic muscle fibers isolated from tibialis anterior. In vitro phosphorylation studies revealed that a large polypeptide of apparent molecular weight of 170 000-150 000 was phosphorylated under basal conditions (3 mM EGTA) in dydy microsomal membranes. The phosphorylation of this polypeptide was not stimulated further by cAMP, calmodulin, cGMP or 12- O-tetradecanoylphorbol 13-acetate (TPA). Under no condition was the corresponding polypeptide phosphorylated at an appreciable rate in normal microsomal membranes. An antibody raised against the voltage-dependent calcium channel reacted, in an immunoblot assay, with a polypeptide, present in both normal and dydy microsomes, which had migration characteristics identical to the phosphorylated 170-150 kDa polypeptide after one- or two-dimensional gel electrophoresis. Additional differences were identified in the phosphorylation of smaller polypeptides of microsomal membranes. When sarcolemmal membranes of normal and dydy muscle were phosphorylated in vitro, no major differences were observed. These results show the existence of an alteration of protein phosphorylation in dystrophic muscle cells in vitro and in vivo, leading to abnormal phosphorylation of the voltage-dependent calcium channel. The possible causes and consequences of this alteration are discussed.

Selective destruction of iron-sulfur centers by heat/ethylene glycol treatment and isolation of Photosystem I core complex

Heat treatment of spinach thylakoids or Photosystem I particles in the presence of ethylene glycol caused the selective destruction of iron sulfur centers F A, F B and F X as judged by low-temperature EPR and flash spectroscopy. Incubation of thylakoids or Photosystem I particles in the presence of 50% ethylene glycol for 5 min selectively destroyed F A and F B at temperatures between 50 and 55°C, and F X between 60 and 70°C. P-700 was destroyed only above 70°C, and electron transport from ascorbate-dichlorophenolindophenol to methyl viologen was inhibited between 35 and 50°C by the same treatment. The destruction of F A and F B occurred at the same temperature range and resulted in the decrease of the decay phase with a 30 ms half-time in re-reduction kinetics of flash-oxidized P-700. This was accompanied by the appearance of the 1 ms decay phase, which reflects reduction of P-700 + by F − X. The 1 ms phase disappeared when F X was destroyed. Photosystem I core complex was isolated by solubilizing the heat/ethylene glycol-treated Photosystem I particles with Triton X-100, followed by sucrose density gradient ultracentrifugation. The complex obtained from 60°C/ethylene glycol-treated preparation lacked the 8 kDa F A/F B polypeptide and was composed of the polypeptides of apparent molecular weight 63, 60 and 5 kDa. This complex showed a small and broadened g = 1.77 F X signal. It is concluded that the heat/ethylene glycol treatment gives a simple and selective degradation-isolation method of Photosystem I reaction center complex.

Properties of IgG subclasses to human cytomegalovirus

The IgG subclass of antiviral antibodies to human cytomegalovirus (CMV) is mainly of IgG1 type. Most CMV seropositive sera also have virus-specific IgG3, but of a lower titre as measured by enzyme-linked immunosorbent assay (ELISA). We studied the reactivity pattern of these two IgG subclasses to CMV structural polypeptides in order to define how virus-specific IgG1 and IgG3 contribute to the neutralization of CMV. Neutralization of CMV was performed with CMV IgG1 and IgG3 separated from CMV seropositive human sera on a protein A Sepharose gel. Both IgG1 and IgG3 have a neutralizing capacity. IgG3 had a 10-fold better neutralizing effect than IgG1 when related to the ELISA titre. In order to analyse the specific reactivities, CMV Towne virion polypeptides were separated by electrophoresis and transferred to nitrocellulose. Using mouse monoclonals to human IgG1 and IgG3 in combination with a biotin-streptavidin system, the reactivities of the subclasses were examined. IgG1 and IgG3 appeared to react with the same structural polypeptides. The strongest IgG1 reactivities were obtained with CMV polypeptides of apparent molecular weights of 145, 80, 64, 56, 52 and 27.5 kDa. The CMV IgG3 reactivity was restricted compared to IgG1, the strongest and most frequent reactivities occurring to polypeptides of 145 and 80 kDa.

Identification of the structural proteins of turkey enteric coronavirus.

SummaryCoronaviruses in the intestinal contents of turkey poults from Quebec flocks with outbreaks of enteritis were detected by electron microscopy. Five isolates were serially propagated in embryonic turkey eggs by inoculation of clarified intestinal contents into the amniotic cavity. Viral particles contained in the intestinal contents of infected embryos were purified by differential and isopycnic centrifugation in sucrose gradients. Intact virions present in fractions of densities 1.18 to 1.20 g/ml were precipitated with trichloroacetic acid and the protein content was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. At least seven polypeptides with molecular weights ranging from 27,000 to 180,000 were regularly detected after electrophoresis of SDS-solubilized virions. Homologous rabbit antisera to turkey coronaviruses and pooled sera from convalescent turkeys immunochemically stained five polypeptides of apparent molecular weights of 95,000, 72–75,000, 66,000, 52,000 and 27,000. A further polypeptide with a molecular weight of 140,000 appeared in the absence of 2-mercaptoethanol and probably represents a dimer of the 66,000 polypeptide. One Quebec isolate differed from the Minnesota strain by two of its polypeptides, but no antigenic variations could be demonstrated amongst the various isolates either by immuno-electron microscopy, hemagglutination inhibition, or enzyme immuno assays on nitrocellulose.

Fibroblast growth factor levels in the whole embryo and limb bud during chick development

A growth factor with properties very similar to fibroblast growth factor (FGF) was detected in the yolk and white of unfertilized chick eggs, and in the limb buds and bodies of Day 2.5 (stage 18)-13 chick embryos using two complementary and highly sensitive biological assays—competition of 125I-a-FGF binding to the FGF receptors of 3T3 cells and stimulation of DNA synthesis in MM14 cells, a permanent mouse skeletal muscle cell line that is dependent upon FGF for proliferation. Further evidence of the similarity of this growth factor to FGF is provided by the finding that biological activity is lost when the material is bound to a heparin-Sepharose column and restored upon elution with 2.5 M NaCl; the 2.5 M NaCl fraction from Day 12 embryos contains several polypeptides of apparent molecular weights 12,500–17,500. The level of FGF in the embryonic chick body is fairly constant between Days 2.5 and 6 (stages 18–29), ranging between 1 and 2 ng FGF/mg protein; but thereafter the level increases so that by Day 13 the body contains about 15 ng FGF/mg protein. In contrast, the level of FGF in the limb bud is higher than that in the rest of the body until Day 5 (stage 27); it then undergoes a transient decrease between Days 6 and 7, after which it increases but remains below the level observed in the remainder of the body.

Molecular Comparison of Pyrophosphate- and ATP-Dependent Fructose 6-Phosphate 1-Phosphotransferases from Potato Tuber

The aim of this work was to compare the molecular properties of pyrophosphate:fructose 6-phosphate 1-phosphotransferase (PFP) and ATP:fructose 6-phosphate 1-phosphotransferase (PFK). Both enzymes were purified to apparent homogeneity from potato tubers (Solanum tuberosum cv Record). Neither PFP nor PFK preparations contained detectable activity of the other enzyme. PFP was composed of two polypeptides of apparent molecular weight 58,000 and 55,700 whereas PFK contained four polypeptides of apparent molecular weight between 46,300 and 53,300. Chemical cleavage of individual PFP and PFK polypeptides gave a different set of fragments for each polypeptide. On Western blots antisera against PFP failed to cross-react with any of the four PFK polypeptides, and antibodies against PFK failed to bind to either of the PFP polypeptides. Antibodies that immunoprecipitate PFP activity had no effect on PFK activity. Conversely, antibodies against the four PFK polypeptides precipitated the activity of PFK, but not that of PFP. This work shows that potato tuber PFP and PFK are composed of distinct, unrelated polypeptides and indicate that interconversion between PFP and PFK is unlikely.

The 140-kDa fibronectin receptor complex is required for mesodermal cell adhesion during gastrulation in the amphibian Pleurodeles waltlii

We have studied the localization and function of a 140-kDa glycoprotein complex implicated in cell adhesion to fibronectin- and laminin-rich extracellular matrices in Pleurodeles waltlii gastrulae. In particular, we have shown that antibodies directed against highly purified avian fibronectin (FN) receptor complex cross-react with two major polypeptides of apparent molecular weights of 140,000 and 100,000 and a third minor component of 90,000. Using sections of embryos or whole mounts, we have also discovered that the putative FN receptor is widely distributed on the early embryonic cell surface. We have also found that the basal surface of the roof of the blastocoel, a region particularly enriched in an extracellular matrix consisting of fibronectin- and laminin-rich fibrils, is rich in receptor complex. We have prepared monovalent Fab' fragments of this antibody and have found that they cause detachment of cells previously attached to substrata coated with fibronectin, and they also arrest gastrulation when injected into the blastocoel of early gastrulae. Thus, it appears that the fibronectin receptor complex plays a significant functional role in cell attachment of gastrula-stage cells in vitro and in cell migration in vivo during gastrulation.

Isolation of a sixth dynein subunit adenosine triphosphatase of Chlamydomonas axonemes.

This study of the axoneme led to the identification of a previously unknown adenosine triphosphatase (ATPase), which is likely a major component of inner dynein arms. The ATPase was isolated from a soluble fraction of axonemes obtained from pf 28, a Chlamydomonas mutant lacking the outer dynein arms. The activity hydrolyzed up to 2.3 mumol of ATP.min-1.mg-1 of protein (at pH 7.2, in the presence of both Ca++ and Mg++), had a sedimentation coefficient of 11S in sucrose gradient, and cosedimented with four polypeptides of apparent molecular weight 325,000, 315,000 140,000, and 42,000. Several arguments indicate that the new ATPase is a component of the inner dynein arms. Three or four polypeptides cosedimenting with the activity belong to a group of axonemal components that are deficient in the axonemes of pf 23 and pf 30, two mutants that display different levels of inner dynein arm deficiency. The 42,000 component is axonemal actin, a subunit of two other inner dynein ATPases. The two polypeptides of molecular weight greater than 300,000 have electrophoretic mobility similar to that of high molecular weight components of outer and inner dynein arms. In spite of some similarities each ATPase isolated from inner or outer arms is composed of a different set of polypeptides. Different ATPases may be required for the modulation of localized sliding of adjacent outer double microtubules in the axoneme.

Identification of identical binding polypeptides for cephalosporins and dipeptides in intestinal brush-border membrane vesicles by photoaffinity labeling

The uptake of a photolabile derivative of the orally effective cephalosporin cephalexin, N-(4-azidobenzoyl)cephalexin, was investigated in brush-border membrane vesicles. The compound was taken up into the intravesicular space and inhibited the active uptake of cephalexin in a concentration-dependent manner. Therefore, this probe interacts with the transport system shared by α-aminocephalosporins and dipeptides. Photoaffinity labeling of brush-border membrane vesicles from rat small intestine with N-(4-azido [3,5,- 3H]benzoyl) derivatives of the cephalosporin cephalexin and the dipeptide glycyl- l-proline resulted in the covalent incorporation of radiaoctivity into membrane polypeptides with apparent molecular weights of 127000, 100000, 94000 and 86000, the polypeptide of molecular weight 127000 being predominantly labeled. The specificity of labeling was demonstrated by a decrease in the labeling of the polypeptide of apparent molecular weight 127000 in the presence of β-lactam antibiotics and dipeptides, whereas glucose, taurocholate or amino acids had not effect on the labeling pattern. These data demonstrate an interaction of cephalosporins and dipeptides with a common membrane protein of molecular weight 127000, which could be a component of the intestinal transport system(s) responsible for the uptake of orally effective cephalosporins and dipeptides.

Identification of the herpes simplex virus protein kinase as the product of viral gene US3.

Previous work has shown that a novel protein kinase is induced after infection of cultured cells with herpes simplex virus type 1 (HSV-1). Separately, it has been reported that the protein encoded by HSV-1 gene US3 shows similarity in its amino acid sequence to members of the protein kinase family of eukaryotes. We have investigated the possibility that these two observations are connected by preparing an antiserum to a synthetic oligopeptide corresponding to the carboxy-terminal eight amino acids of the US3 protein. This antiserum reacted on immunoblots with a polypeptide of apparent molecular weight 68,000 from extracts of cells which had been infected with HSV-1. The antiserum also reacted strongly with a 68,000 molecular weight species from a preparation of the novel HSV-1 protein kinase which had been extensively purified and resolved from other protein kinases. In addition, the purified preparation phosphorylated a protein species, also of 68,000 apparent molecular weight, when incubated with [gamma-32P]ATP. These data are consistent with gene US3 encoding the novel protein kinase induced after infection of cells with HSV-1.

Elicitor induction of the synthesis of a novel lectin-like arabinosylated hydroxyproline-rich glycoprotein in suspension cultures of Phaseolus vulgaris L.

A novel lectin-like glycoprotein which accumulates in response to fungal elicitor action has been characterised in endomembranes from suspension cultures of French bean (Phaseolus vulgaris L.). The lectin, which has specificity towards N-acetylglucosamine oligomers, consists of a polypeptide of apparent molecular weight (Mr) 31 000 which is rich in glycine and contains 6.7% hydroxyproline O-linked to arabinose-containing oligosaccharides to give a glycoprotein of Mr 42500. A dual-labelling technique has been used to identify changes in the synthesis of the glycoprotein in cells exposed to fungal elicitor molecules. Thus, incorporation of [(14)C]proline into membranes in vivo and of [1(-3)H]arabinose from uridine 5'-diphosphate [1(-3)H]arabinose in vitro and analysis by isoelectric focussing-polyacrylamide gel electrophoresis gave absolute correspondence of the labelled isoform of the glycoprotein. Having established the absence of contaminating polypeptides, subsequent analysis of microsomal fractions bysodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the peak of sythesis of the Mr-42500 glycoprotein occurred 4 h after the addition of fungal elicitor. The changes in the level of incorporation into the glycoprotein monomers were concomitant with increases in the activity of prolyl hydroxylase (EC 1.14.11.2)Incorporation of [(14)C]proline and its subsequent post-translational modification to hydroxyproline in microsomal polypeptides was followed by rapid transfer into the wall with an average t 1/2 of about 7 min. The Mr-42500 glycoprotein was rapidly transferred out of the endomembrane fraction with a t 1/2 of 2 min and could be detected in wall fractions where it became progressively less extractable. The glycoprotein, which clearly differs from bean extensin, accounts for up to 40% of the hydroxyproline newly exported in response to elicitor action. The lectin, which resembles those found in the Solanaceae and which is coinduced with enzymes of phytoalexin synthesis, may play some role in disease resistance.

Generation and properties of the glycoprotein E-related 32K/34K/35K and 55K/57K polypeptides encoded by herpes simplex virus type 1.

A hybridoma line was isolated which produced antibody reacting with polypeptides of apparent molecular weights 32,000, 34,000 and 35,000 (32K/34K/35K) and 55,000 and 57,000 (55K/57K). These were sulphated glycoproteins that have previously been found in the medium of herpes simplex virus type 1 (HSV-1)-infected cells. By tryptic peptide mapping and serological cross-reactions the polypeptides were shown to be related to HSV-1 glycoprotein E (gE-1) but they lacked the Fc binding function. The 32K/34K/35K and 55K/57K polypeptides were not found in the medium of HSV-1-infected cells incubated in serum-free medium. They could be generated in vitro from purified gE-1 in the presence of serum. It is likely that 32K/34K/35K and 55K/57K are derived from gE-1 by the action of serum proteases.

Sucrose regulation of protein synthesis in pea root meristem cells

The enhanced synthesis of a polypeptide of apparent molecular weight of 93,000 daltons in apical meristem cells of excised pea roots appears to be a specific response to low sugar levels in these cells. Following excision of roots, the levels of soluble sugars in the meristems drop precipitously, this drop preceding the switch to selective incorporation of 3H-leucine, detected by SDS-PAGE fluorography, into the polypeptide; removal of cotyledons from otherwise intact seedlings also results in an increase, in the meristem, in the relative amount of a polypeptide of the same apparent molecular weight. When exogenous sucrose is provided to starved, excised roots, the preferential incorporation of 3H-leucine into the 93,000 dalton polypeptide is greatly reduced, indicating an immediate and specific repression of its synthesis by sucrose. Finally, exposure of starved meristems to elevated temperature results in a switch to incorporation of labeled leucine into typical heat-shock proteins, rather than into the sucrose-regulated polypeptide.