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The structure of the mutant dihydrofolate reductase from Streptococcus faecium. Partial sequence and order of the limited tryptic and cyanogen bromide peptides.

Authors
  • Gleisner, J M
  • Peterson, D L
  • Blakley, R L
Type
Published Article
Journal
The Journal of biological chemistry
Publication Date
Jul 10, 1975
Volume
250
Issue
13
Pages
4937–4944
Identifiers
PMID: 1150647
Source
Medline
License
Unknown

Abstract

The major form of dihydrofolate reductase from a methotrexate-resistant mutant (strain A) of Streptococcus faecium var. Durans has been purified on a large scale. Amino acid analysis of this form of the enzyme (isoenzyme 2) reveals an absence of cystine or cysteine, and sedimentation studies indicate a molecular weight of 20,800. The NH2-terminal sequence was determined by Edman degradation of the intact protein and the COOH terminus by selective tritiation and by carboxypeptidase treatment. After the action of trypsin on the citraconylated protein, seven of the expected nine peptides were purified from the digest, and after cyanogen bromide treatment of the unmodified protein, all seven of the anticipated peptides were isolated. The amino acid composition of all of these peptides has been established as well as their complete or partial sequences. From the results it was possible to order these peptides within the sequence and to establish the sequence of the NH2-terminal 60 residues and the COOH-terminal 11 residues.

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