Improved recovery of methionine after acid hydrolysis using mercaptoethanol

Swine lipoproteins and atherosclerosis. Changes in the plasma lipoproteins and apoproteins induced by cholesterol feeding

Cholesterol feeding in miniature swine resulted in a hypercholesterolemia with a distinctive hyperlipoproteinemia and the subsequent development of atherosclerosis. Alterations in the type and distribution of plasma lipoproteins induced by cholesterol feeding were as follows: (a) the occurrence of beta-migrating lipoproteins (B-VLDL) as well as very low density lipoproteins in the d less than 1.006 ultracentrifugal fraction; (b) an increased prominence of the intermediate lipoproteins (d = 1.006-1.02); (c) an increased prominence of low density lipoproteins; and (d) the occurrence of a distinctive lipoprotein with alpha mobility which was referred to as HDLc (cholesterol induced). Characterization of the various plasma lipoproteins included chemical composition, size by electron microscopy, and apoprotein content. The B-VLDL resembled the beta-migrating lipoproteins of human Type III hyperlipoproteinemia and contained a prominent protein equivalent to the arginine-rich apoprotein in addition to the B apoprotein, apo-A-I, and the fast-migrating apoproteins (apo-C). The HDLc were rich in cholesterol, ranged in size from 100 to 240 A in diameter, and contained the arginine-rich apoprotein and apo-A0I but lacked the B apoprotein. The arginine-rich apoproteins isolated from B-VLDL and HDLc by gel chromatography were similar in amino acid analyses, with glutamic acid as their amino-terminal residue. The occurrence of a spectrum of cholesterol-rich lipoproteins which contained the arginine-rich apoprotein with the occurrence of accelerated atherosclerosis suggested an interesting, although speculative, association.

Change of cytochrome c structure during development of the mouse

The structure of cytochrome c during mouse development is investigated. For this purpose the amino acid sequence of cytochrome c of the adult mouse had to be determined. The structure of cytochrome c of adult differentiated mouse cells differs in two amino acid residues from the known amino acid sequence of rabbit cytochrome c. No indication of different forms of cytochrome c in the adult differentiated cells was obtained. The structure of cytochrome c from 11.5-day-old mouse embryos is identical with that of adult mouse tissues. Since germ cells after meiotic division are the immediate precursors of a new individual, the structure of cytochrome c from sperm-containing mice testes was investigated. By means of chromatography of the cytochrome c and of peptide maps and amino acid analyses of its tryptic peptides, it is shown that mouse testis contains two isocytochromes c in about equal amount. The structure of one of these two isocytochromes c is identical with the structure of the adult-type cytochrome c of mouse. The testis-specific cytochrome c, which is assumed to be located in the sperm cells, differs in 13 of its 104 amino acid residues from the adult-type cytochrome c. From comparison of the primary and the spatial structures of the adult-type and the sperm-type isocytochromes c with the known structures of cytochrome c of more than 65 different species it is concluded that the duplication of the cytochrome c structural gene, causing the existence of the two ontogenetic-specific isocytochromes c in mouse, has occurred early in the evolution of eucaryotes.

Lipid-protein interactions in high density lipoproteins

Delipidated high density lipoprotein (apo-HDL), isolated apolipoproteins apoA-I and apoA-II, S-carboxymethylated apoA-II, apoC-III, the NH(2)- and COOH-terminal CNBr peptides of apoA-II, and the COOH-terminal CNBr peptide of apoA-I were recombined in vitro with [N-C(3)H(3)-choline]phosphatidylcholine (PC) and [N-(14)CH(3)-choline]sphingomyelin (SPM). The lipid-protein complexes were analyzed by ultracentrifugal flotation, agarose gel chromatography and circular dichroism. ApoHDL, apoA-II, and S-carboxymethylated apoA-II readily recombined with PC or SPM to form particles that were similar in size to native HDL. The COOH- but not the NH(2)-terminal CNBr peptide of apoA-II recombined with lipid. ApoA-I and the COOH-terminal CNBr peptide of apoA-I, however, recombined with PC or SPM to only a limited extent, suggesting that protein-protein interactions between apoA-I and apoA-II are important in the integration of apoA-I into recombined lipoprotein particles. Analysis of the recombined lipid-protein complexes by circular dichroism indicated that there was an increase in helical structure concomitant with lipid-protein binding. The reconstituted particles had many of the physical and chemical properties of the native lipoprotein.

Amino acid sequences around the cysteine residues of rabbit muscle triose phosphate isomerase

1. The nature of the subunits in rabbit muscle triose phosphate isomerase has been investigated. 2. Amino acid analyses show that there are five cysteine residues and two methionine residues/subunit. 3. The amino acid sequences around the cysteine residues have been determined; these account for about 75 residues. 4. Cleavage at the methionine residues with cyanogen bromide gave three fragments. 5. These results show that the subunits correspond to polypeptide chains, containing about 230 amino acid residues. The chains in triose phosphate isomerase seem to be shorter than those of other glycolytic enzymes.

Metabolic fate of cysteine and methionine in rumen digesta

Estimates were obtained of the extent to which cysteine and methionine were incorporated into the protein of the microbes of rumen digesta without prior degradation and resynthesis. By using the amino acids labeled with both (35)S and (14)C, it was observed that a large proportion of the (35)S appeared in the sulfide pool and of the (14)C appeared in volatile fatty acids. By isolating the appropriate amino acid, obtaining the (14)C to (35)S ratio, and comparing this with the ratio in the added amino acid, the degree of direct incorporation was calculated. For cysteine it was estimated that at most 1% and for methionine, at most 11% of the amino acid in the free pool was incorporated unchanged into microbial protein. As a consequence of these findings, it is considered that the method for measuring microbial protein synthesis in rumen digesta based upon incorporation of (35)S from the free sulfide pool is not seriously affected by direct utilization of sulfur amino acids arising from dietary sources.

Amino acid sequence of salmon ultimobranchial calcitonin

Salmon ultimobranchial calcitonin has been isolated and rendered pure, as demonstrated by several chemical criteria. Its amino acid sequence was determined by means of manual Edman degradation of the intact molecule and of several peptide subfragments. Results of automated degradation provided confirmation of the structure. The salmon molecule possesses, in common with other calcitonins, a 32-amino acid peptide chain terminating in prolinamide and containing half-cystine residues at positions 1 and 7. Although the sequence of the salmon hormone differs considerably from that of the porcine, bovine and human calcitonins, the four hormones are homologous in 9 of 32 positions. The much higher biological potency possessed by the salmon calcitonin makes it of particular interest for future structure function studies.