Rod Substructures Research Articles

Cyanobacterial phycobilisomes. Role of the linker polypeptides in the assembly of phycocyanin.

The phycocyanin-containing segments of the rod substructures of Anabaena variabilis phycobilisomes consist of complexes of phycocyanin with "linker" polypeptides of 27,000 and 32,500 daltons (Yu, M.-H., Glazer, A. N., and Williams, R. C. (1981) J. Biol. Chem. 256, 13130-13136). Complexes (alpha beta)3.27,000, (alpha beta)3.32,500, (alpha beta)6.27,000, [(alpha beta)6.32,500]n, (alpha beta)6.27,000 - (alpha beta)6.32,500 were prepared, where alpha beta represents a monomer of phycocyanin, and 27,000 and 32,500 represent the 27,000- and 32,500-dalton polypeptides, respectively. Tryptic digestion of (alpha beta)3.32,500 leads to a stable (alpha beta)3.28,000 complex which does not form higher aggregates. The 32,500 polypeptide is stable to trypsin in the [(alpha beta)6.32,500]n and (alpha beta)6.27,000 - [(alpha beta)6.32,500]n=1.2 aggregates. Upon trypsin treatment of all 27,000 still assembled into higher aggregates, (alpha beta)6.21,0900 and (alpha beta)6.21,000 - (alpha beta)6.32,500. The spectroscopic properties of phycocyanin-linker polypeptide complexes were not modified by the tryptic cleavages. These results show that the 32,500 polypeptide has two distinct functional domains, a 28,000 portion necessary to the stabilization of a trimeric phycocyanin complex and a 4,500 domain which links consecutive phycocyanin hexamers in the rod substructure. The 27,000 polypeptide likewise has two distinct functional domains: a 21,000 domain stabilizes a trimeric phycocyanin complex, a 6,000 domain is exposed in all of the assembly forms examined. From these and earlier studies, it is concluded that the 6,000 domain functions in the attachment of the rod substructures to the core of the phycobilisome.

Rod substructure in cyanobacterial phycobilisomes: analysis of Synechocystis 6701 mutants low in phycoerythrin.

Synechocystis 6701 phycobilisomes contain phycoerythrin, phycocyanin, and allophycocyanin in a molar ratio of approximately 2:2:1, and other polypeptides of 99-, 46-, 33.5-, 31.5-, 30.5-, and 27-kdaltons. Wild-type phycobilisomes consist of a core of three cylindrical elements in an equilateral array surrounded by a fanlike array of six rods each made up of 3-4 stacked disks. Twelve nitrosoguanidine-induced mutants were isolated which produced phycobilisomes containing between 0 and 53% of the wild-type level of phycoerythrin and grossly altered levels of the 30.5- and 31.5-kdalton polypeptides. Assembly defects in these mutant particles were shown to be limited to the phycoerythrin portions of the rod substructures of the phycobilisome. Quantitative analysis of phycobilisomes from wild-type and mutant cells, grown either in white light or chromatically adapted to red light, indicated a molar ratio of the 30.5- and 31.5-kdalton polypeptides to phycoerythrin of 1:6, i.e., one 30.5- or one 31.5-kdaltons polypeptide per (alpha beta)6 phycoerythrin hexamer. Presence of the phycoerythrin-31.5-kdalton complex in phycobilisomes did not require the presence of the 30.5-kdalton polypeptide. The converse situation was not observed. These and earlier studies (R. C. Williams, J. C. Gingrich, and A. N. Glazer. 1980. J. Cell Biol. 85:558-566) show that the average rod in wild type Synechocystis 6701 phycobilisomes consists of four stacked disk-shaped complexes: phycocyanin (alpha beta)6-27 kdalton, phycocyanin (alpha beta)6-33.5 kdalton, phycoerythrin (alpha beta)6-31.5 kdalton, and phycoerythrin-30.5 kdalton, listed in order starting with the disk proximal to the core.

Cyanobacterial phycobilisomes. Phycocyanin assembly in the rod substructures of anabaena variabilis phycobilisomes.

Phycocyanin complexes with "linker" polypeptides (Lundell, D. J., Williams, R. C., and Glazer, A. N. (1981) J. Biol. Chem. 256, 3580-3592) of 27 and 32.5 kilodaltons have been isolated from dissociated Anabaena variabilis phycobilisomes. In 0.05 M phosphate at pH 7.0, these "trimeric" complexes have the molar composition (alpha beta)3 . 27,000 and (alpha beta)3 . 32,500, where alpha and beta are the subunits of phycocyanin and 27,000 and 32,500 denote single copies of the linker polypeptides. The (alpha beta)3 . 27,000 and (alpha beta)3 . 32,500 complexes have lambda max at 638 and 629 nm and fluorescence emission maxima at 651 and 646 nm, respectively. In 0.6 M phosphate at pH 8.0, the (alpha beta)3 . 27,000 complex forms an (alpha beta)6 . 27,000 disc-shaped aggregate as seen in the electron microscope, whereas the (alpha beta)3 . 32,500 complex forms discs, (alpha beta)6 . 32,500, and stacked disc rods of varying lengths. The former material, containing the 27,000 polypeptide, when mixed with the (alpha beta)6 . 32,500 discs, limits their assembly into rods. The spectroscopic properties of the discs and rods assembled in vitro indicate that energy transfer in phycobilisome rod substructures proceeds from (alpha beta)6 . 32,500 discs to the (alpha beta)6 . 27,000 disc proximal to the core and thence to the core.

Molecular architecture of a light-harvesting antenna. Comparison of wild type and mutant Synechococcus 6301 phycobilisomes.

Phycobilisomes of the cyanobacterium Synechococcus 6301 contain C-phycocyanin and allophycocyanin in a molar ratio of approximately 3.8:1, a minor biliprotein, allophycocyanin B, and nonpigmented polypeptides of 75, 33, 30, and 27 kilodaltons. A nitrosoguanidine-induced mutant AN112 produces altered phycobilisomes with the molar ratio of C-phycocyanin to allophycocyanin reduced to approximately 1.4:1 and without any of the 33- and 30-kilodalton polypeptides. The mutant and wild type phycobilisomes contain the same molar amount of the 75- and 27-kilodalton polypeptides relative to allophycocyanin. As seen by electron microscopy, the allophycocyanin-containing core of the mutant and of the wild type phycobilisomes appears the same. In some views of the core, each of the two core units in the mutant particles can be seen to consist of four discs approximately 3 nm thick. In wild type phycobilisomes five or six rods, made up of two to six stacked discs (11.5 X 6 nm) are attached to the core. In the mutant, no such rods are seen; rather, single disc-shaped elements, ranging from two to six in number, are found attached. Spectroscopic measurements show that the assembly form of phycocyanin in the mutant phycobilisomes differs from that in the wild type particles but reveal no difference in the organization of the core elements. These results indicate that the portions of the rod substructures of wild type phycobilisomes, beyond the disc proximal to the core, are made up of phycocyanin and the 33- and 30-kilodalton polypeptides. Emission from phycocyanin is a significant component in the fluorescence from isolated Synechococcus 6301 phycobilisomes and indicates an upper limit of 94% for the efficiency of energy transfer from phycocyanin to allophycocyanin and allophycocyanin B in these particles.

Statistics of branched polymers composed of rod substructures: a model for fibrin before clot formation

The aggregation process of fibrin formation is treated statistically on the basis of a special model. This model takes into consideration (a) a rod-like end-to-end aggregation of the activated fibrinogen monomers, (b) a lateral aggregation of the rod-like strands, and (c) branching after a certain end-to-end aggregation. Application of Gordon's cascade theory allowed the calculation of the molecular weight M w , the mean square radius of gyration < S 2>, and the angular dependence of the scattered light, where the strong non-Gaussian behaviour due to the rod-like substructure is taken into account. The theory gives a good description of the experimentally observed molecular weight dependence of < S 2>, and of the experimental scattering curves. In particular, the transition from the rod-like behaviour to that of the branched structure is very satisfactorily represented by the present theory and the underlying model.

Chloroma (granulocytic sarcoma) without evidence of leukemia: facilitated light microscopic diagnosis

Localized tumors composed of immature cells of the myelogenous series have been recognized for many years as an uncommon manifestation of granulocytic leukemia. The histologic diagnosis of chloroma (granulocytic sarcoma) may be extremely difficult when the myeloblastic cells are poorly differentiated and the tumor lacks the characteristic green color. The diagnostic difficulty may be further compounded when the granulocytic sarcoma develops before there is peripheral blood or bone marrow evidence of leukemia. Previous criteria for the diagnosis of chloroma have been ambiguous because of the capricious nature of the hydroperoxidase activity and the lack of definitive histochemical criteria. In this case, a combination of Sudan black B and myeloperoxidase histochemical staining and ultrastructural evaluation was applied. The light microscopic histochemical studies suggested the presence of Phi bodies and rods both in the formalin-fixed tumor and in the cells derived from the subsequent pleural effusion; this was confirmed by electron microscopy, which demonstrated the peridicity of the crystalline rod substructure. These observations show that light microscopic histochemical studies can facilitate the diagnosis of granulocytic sarcoma or chloroma in the absence of peripheral blood or bone marrow manifestations of leukemia.

Chloroma (Granulocytic Sarcoma) Without Evidence of Leukemia: Facilitated Light Microscopic Diagnosis

AbstractLocalized tumors composed of immature cells of the myelogenous series have been recognized for many years as an uncommon manifestation of granulocytic leukemia. The histologic diagnosis of chloroma (granulocytic sarcoma) may be extremely difficult when the myeloblastic cells are poorly differentiated and the tumor lacks the characteristic green color. The diagnostic difficulty may be further compounded when the granulocytic sarcoma develops before there is peripheral blood or bone marrow evidence of leukemia. Previous criteria for the diagnosis of chloroma have been ambiguous because of the capricious nature of the hydroperoxidase activity and the lack of definitive histochemical criteria. In this case, a combination of Sudan black B and myeloperoxidase histochemical staining and ultrastructural evaluation was applied. The light microscopic histochemical studies suggested the presence of Phi bodies and rods both in the formalin-fixed tumor and in the cells derived from the subsequent pleural effusion; this was confirmed by electron microscopy, which demonstrated the periodicity of the crystalline rod substructure. These observations show that light microscopic histochemical studies can facilitate the diagnosis of granulocytic sarcoma or chloroma in the absence of peripheral blood or bone marrow manifestations of leukemia.