Search

1. A new method is described for ;fingerprinting' cysteic acid peptides derived from the disulphide bridges of proteins. Cystine peptides are separated by paper electrophoresis and oxidized on paper by performic acid vapour. Electrophoresis at right angles to the first direction produces parallel groups of cysteic acid peptides lying off a diagonal. This ;fingerprint' reveals the way in which the cysteic acid peptides were originally joined in the protein. 2. The method allows a very easy selective purification of cysteic acid peptides. 3. By applying this method to bovine chymotrypsinogen A, we found that the half-cystine residues were linked 1-122, 42-58, 136-201, 168-182 and 191-220.

Reinvestigation of the amino acid sequence of bovine chymotrypsinogen A suggests that the amino acid sequence at the N-terminus of the B-chain (residues 16-19) is -Ile-Val-Asn-Gly- rather than -Ile-Val-Gly-Asp- and that Ser-215 should be deleted.

1. A chymotryptic digest of the protein fraction U.S.3. from oxidized wool was separated into 51 peptide fractions by chromatography on a column of cation-exchange resin. 2. The less acidic fractions were separated into their component peptides by a combination of cation-exchange-resin chromatography, paper chromatography and paper electrophoresis. 3. The amino acid sequences of 34 of these peptides were elucidated, and those of 14 others partially determined. 4. Overlaps between the tryptic and chymotryptic peptides from fraction U.S.3 have enabled ten extended amino acid sequences to be deduced, the longest containing 20 amino acid residues. 5. The relevance of the results to the structures of the helical and non-helical regions of wool is discussed.

Peptide A, the C-terminal cyanogen bromide fragment of thioredoxin, was degraded with chymotrypsin and pepsin. Partial sequences of 12 chymotryptic and 6 peptic peptides and the N-terminal tryptic peptide of trifluoro-acetylated peptide A were determined. The results were used to establish the order of the previously described tryptic peptides of peptide A and lead to the complete amino acid sequence of peptide A. Previous experiments had established the amino acid sequence of peptide B, the N-terminal cyanogen bromide fragment of thioredoxin and the present results thus give the complete amino acid sequence of thioredoxin from Escherichia coli B. The molecule contains 108 residues in a single polypeptide chain with a molecular weight of 11,657 as calculated from the sequence. The functional group of the protein occurs in position 32 to 35 and consists of a disulfide bridge formed by two half-cystine residues separated by a glycine and a proline residue. No metals were found as part of the functional group. [ABSTRACT FROM AUTHOR]

Using automated stepwise Edman degradation of suitable overlapping peptides, the complete amino acid sequence of the 268 residue peptida α1-CB7 from calf skin collagen was determined. The preparation and ordering of the chymotryptic, tryptic and thermolytic peptides is described in the preceding paper. As shown previously for other peptides from the helical region of collagen, glycine appears in every third position and proline is present in high amount. Hydroxylation of proline to 4-hydroxyproline and lysine to hydroxylysine only occurred in the Y position of the tripeptide unit Gly-X-Y. Non-random distribution of other amino acids between the X and Y positions was also observed. [ABSTRACT FROM AUTHOR]