Premium
The DNA replication inhibitor microcin B17 is a forty‐three‐amino‐acid protein containing sixty percent glycine
Author(s) -
Davagnino Juan,
Herrero Marta,
Furlong Dierdre,
Moreno Felipe,
Kolter Roberto
Publication year - 1986
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.340010305
Subject(s) - amino acid , biochemistry , plasmid , gene product , peptide sequence , gene , escherichia coli , biology , glycine , nucleic acid sequence , mutant , signal peptide , structural gene , microbiology and biotechnology , chemistry , gene expression
Abstract Microcin B17 is a low‐molecular‐weight protein that inhibits DNA replication in a number of enteric bacteria. It is produced by bacterial strains which harbor a 70‐kilobase plasmid called pMccB17. Four plasmid genes (named mcbABCD ) are required for its production. The product of the mcbA gene was identified by labelling minicells. The mcbA gene product was slightly larger when a mutation in any of the other three production genes was present. This indicates that these genes are involved in processing the primary mcbA product to yield the active molecule. The mcbA gene product predicted from the nucleotide sequence has 69 amino acids including 28 glycine residues. Microcin B17 was extracted from the cells by boiling in 100 mM acetic acid, 1 mM EDTA, and purified to homogeneity in a single step by high‐performance liquid chromatography through a C18 column. The N‐terminal amino acid sequence and amino acid composition demonstrated that mcbA is the structural gene for microcin B17. The active molecule is a processed product lacking the first 26 N‐terminal residues. The 43 remaining residues include 26 glycines. While microcin B17 is an exported protein, the cleaved N‐terminal peptide does not have the characteristic properties of a “signal sequence,” which suggests that it is secreted by a mechanism different from that used by most secreted proteins of E. coli .