Altered Amino Acid Composition Research Articles

Measurement of superoxide formation in isolated cardiac myocytes

A study has been made of the changes in the constituent proteins of a sample of sulfur-deficient human hair (trichothiodystrophy, TTD) which has a cystine content less than 50% of normal. The constituent low-sulfur proteins, although increased in amount, appear normal (apart from the absence of one minor component) as they contain the same array of subunit polypeptides covering the same range of molecular weights and isoelectric points as normal hair. In contrast, the high-sulfur proteins not only were decreased from the normal 40–45% to less than 10% but the proteins were on average smaller, had a lower than normal cystine content, and had a greatly altered amino acid composition. Fractionation followed by two-dimensional electrophoresis of the fractions revealed that the TTD high-sulfur proteins had lost the large heterogeneous group of ultrahigh-sulfur proteins and at least 8 major high-sulfur protein components but had acquired at least 22 components of lower than normal cystine content, which are either not present in normal human hair or are present at levels too low for detection. It is suggested, on the basis of nutritional studies on sheep and humans, that the loss of the ultrahigh-sulfur proteins is due to the presence of a sulfur-deficiency state, presumably of metabolic origin. The changes in the other high-sulfur proteins may be due to the mutation having affected the operation of a regulatory gene for high-sulfur proteins, as such changes do not occur in wool or hair as a result of dietary manipulation.

A Comparison of the Proteins of Normal and Trichothiodystrophic Human Hair

A study has been made of the changes in the constituent proteins of a sample of sulfur-deficient human hair (trichothiodystrophy, TTD) which has a cystine content less than 50% of normal. The constituent low-sulfur proteins, although increased in amount, appear normal (apart from the absence of one minor component) as they contain the same array of subunit polypeptides covering the same range of molecular weights and isoelectric points as normal hair. In contrast, the high-sulfur proteins not only were decreased from the normal 40–45% to less than 10% but the proteins were on average smaller, had a lower than normal cystine content, and had a greatly altered amino acid composition. Fractionation followed by two-dimensional electrophoresis of the fractions revealed that the TTD high-sulfur proteins had lost the large heterogeneous group of ultrahigh-sulfur proteins and at least 8 major high-sulfur protein components but had acquired at least 22 components of lower than normal cystine content, which are either not present in normal human hair or are present at levels too low for detection. It is suggested, on the basis of nutritional studies on sheep and humans, that the loss of the ultrahigh-sulfur proteins is due to the presence of a sulfur-deficiency state, presumably of metabolic origin. The changes in the other high-sulfur proteins may be due to the mutation having affected the operation of a regulatory gene for high-sulfur proteins, as such changes do not occur in wool or hair as a result of dietary manipulation.

A-IMilano apoprotein. Decreased high density lipoprotein cholesterol levels with significant lipoprotein modifications and without clinical atherosclerosis in an Italian family.

Significant hypertriglyceridemia with a very marked decrease of high density lipoproteins (HDL)-cholesterol levels (7-14 mg/dl) was detected in three members (father, son, and daughter) of an Italian family. The three affected individuals did not show any clinical signs of atherosclerosis, nor was the atherosclerotic disease significantly present in the family. Lipoprotein lipase and lecithin:cholesterol acyltransferase activites were normal or slightly reduced. Morphological and compositional studies of HDL in the subjects showed a significant enlargement of the lipoprotein particles (approximately 120 vs. approximately 94 A for control HDL) and a concomitant increase in the triglyceride content. Analytical isoelectric focusing of HDL apoproteins provided evidence for multiple isoproteins in the apoprotein(apo)-A-I range, with nine different bands being detected instead of the usual four bands observed in normal subjects. Two-dimensional immunoelectrophoresis against apo-A antiserum indicated a clear reduction of apo-A in the alpha electrophoretic region, with splitting of the protein "peak." The observation in otherwise clinically healthy subjects of hypertriglyceridemia, reduced HDL-cholesterol, and marked apoprotein abnormalities, without a significant incidence of atherosclerotic disease in the family suggests this is a new disease entity in the field of lipoprotein pathology, very probably related to an altered amino acid composition of the apo-A-I protein (see Weisgraber et al. 1980. J. Clin. Invest. 66: 901-907).

Defective cleavage of a precursor polypeptide in a temperature-sensitive mutant of avian sarcoma virus

Noninfectious virus particles released at the nonpermissive temperature from cells infected with the temperature-sensitive mutant LA334 of avian sarcoma virus B77 have been investigated. These particles bud atypically, have improperly formed core structures, are heterogeneous in size and on a density gradient, and are also slightly more dense than wild-type virus. One major new viral-coded protein of 23,000 molecular weight, p23, and several minor abnormally cleaved and/or partially degraded viral-specific peptides are incorporated into the noninfectious particles. As a result of tryptic peptide analyses of some of these new proteins, it could be proposed that the defect of this mutant is in the cleavage of pr76, the 76,000 molecular weight precursor for the internal viral proteins of avian tumor viruses (ATV). In addition, we have detected one methionine-labeled viral tryptic peptide with an altered amino acid composition, which may represent the site of the temperature sensitive lesion.

The interaction of serum and arterial lipoproteins with elastin of the arterial intima and its role in the lipid accumulation in atherosclerotic plaques.

Arterial elastin appears to be a proteinlipid complex with the lipid component being bound to elastin peptide groups. In atherosclerotic lesions the lipid content of elastin increases progressively with increasing severity of atherosclerosis. The increases in the lipid content of plaque elastin are mainly due to large increases in cholesterol with about 80% of the cholesterol being cholesterol ester. This deposition of cholesterol in elastin accounts for a substantial part of the total cholesterol accumulation in atherosclerotic lesions of all stages. The present in vitro study suggests that the mechanism involved in the deposition of lipids in arterial elastin may be an interaction of the elastin protein with serum or arterial low density or very low density lipoproteins (LDL and VLDL) resulting in a transfer of lipids, but not of lipoprotein protein to the elastin. No significant lipid transfer occurred from the high density lipoproteins or chylomicrons. The amount of lipid taken up by plaque elastin was strikingly higher than by normal elastin and consisted mainly of cholesterol with over 80% of the cholesterol being cholesterol ester. The precondition for the lipid accumulation in plaque elastin appeared to be an altered amino acid composition of the elastin protein consisting of an increase in polar amino acids and a reduction in cross-linking amino acids. Subsequent treatment of lipoprotein-incubated arterial elastin with hot alkali and apolipoproteins did not reverse the binding of lipoprotein lipid to diseased elastin.

Effect of N Fertilization and Simazine on Yield, Protein, Amino‐acid Content, and Carotenoid Pigments of Coastal Bermudagrass1

AbstractReports of increased protein levels in several plant species with simazine treatments prompted this study of the response of coastal bermudagrass (Cynodon dactylon L. Pers.) to simazine. Simazine was applied at rates ranging from 0 to 4.5 kg/ha on an old sod of coastal bermudagrass. Additional variables were N fertilization (56 to 672 kg/ha) and cutting frequency (3 and 6 weeks). Nitrogen fertilization and cutting frequency significantly affected yields of dry matter and protein. Simazine applications had no effect on dry‐matter yield, protein yield, or protein percentage. Carotene and xanthophyll contents of the grass increased with an increase in N fertilization from 336 to 672 kg/ha. Carotene content of the grass tended to increase due to simazine treatment with 360 kg/ha N and to decrease with 672 kg/ha. Samples were analyzed for 15 amino acids, and differences between the amino‐acid profile of the protein from check and simazine‐treated samples suggested that simazine may alter amino acid composition of protein.

The Metabolizable Energy of Opaque-2 and Floury-2 Corn for the Chick

Two mutant genes, Opaque-2 and Floury-2, have been shown to produce changes in the appearance and in the amino acid composition of corn endosperm (Mertz et al., 1964; Nelson et al., 1965). The superior nutritive value of Opaque-2 corn for the rat (Mertz, 1966) and pig (Cromwell et al., 1967) and the superior nutritive value of Floury-2 corn for the chick (Cromwell et al., 1968) have been demonstrated. These effects have been attributed to the altered amino acid composition of the mutant corns. It was considered desirable to compare the metabolizable energy values of these mutant corns with that of normal corn.PROCEDURETwo trials, each involving 112 two-week old Hubbard White Mountain male chicks randomly assigned to four experimental treatments, with seven birds assigned to each of four replications per treatment, were conducted to determine the metabolizable energy of normal, Opaque-2 and Floury-2 corns for the chick. The Opaque-2 .

The Unsuitability of Some Viruliferous Plants as Hosts for the Green Peach Aphid, Myzus persicae

Significant differences were observed in the rates of multiplication of Myzus persicae (Sulzer) when reared on healthy and on cucumber mosaic virus-infected seedlings of Nicotiana tabacum L., Gomphrena globosa L., and Zinnia elegans Jacq. Aphid populations after 8 to 12 days were 2.10, 2.04 and 4.77 times larger on healthy than on the diseased seedlings, respectively. It is suggested that the altered amino acid composition of the viruliferous plants rendered them unsuitable as hosts.

Vulnerability of nucleic acids in mutant staphylococci with impaired respiration.

SUMMARY: Mutant staphylococci with impaired respiration, induced by ultraviolet radiation, were used for testing various inhibitors with already known mechanisms of action. Inhibitors of protein synthesis (the tetracyclins) affected the growth of parent and mutant cultures to the same degree. To the inhibitors of cell-wall synthesis (the penicillins) mutant staphylococci were more resistant than the parents; this was related to the altered amino acid composition of cell-wall material in the mutants. On the other hand, the mutants were much more vulnerable than parents to the action of inhibitors which affected the nucleic acids—namely, mitomycin C (x 50 times), actinomycin C (x 50). trypaflavine (x 300), nitrogen mustards (x 10-20). A specific thymine synthetase inhibitor (5-fluorodeoxyuridine) strongly inhibited the growth of parent staphylococci, but did not at all inhibit the growth of mutants. This points to some deficiency in the enzymic mechanism of synthesis of thymine in the DNA of mutants. Experiments with 5-bromodeoxyuridine suggest that the mutant staphylococci lacked the enzymic mechanism necessary for effective incorporation of halogenated pyrimidines into the DNA precursor pool.