Self-Protection against Cell Wall Hydrolysis in Streptococcus milleri NMSCC 061 and Analysis of the Millericin B Operon
- 1 September 2001
- journal article
- Published by American Society for Microbiology in Applied and Environmental Microbiology
- Vol. 67 (9), 3888-96
- https://doi.org/10.1128/aem.67.9.3888-3896.2001
Abstract
Streptococcus milleri NMSCC 061 produces an endopeptidase, millericin B, which hydrolyzes the peptide moiety of susceptible cell wall peptidoglycan. The nucleotide sequence of a 4.9-kb chromosomal region showed three open reading frames (ORFs) and a putative tRNA(Leu) sequence. The three ORFs encode a millericin B preprotein (MilB), a putative immunity protein (MilF), and a putative transporter protein (MilT). The milB gene encodes a 277-amino-acid preprotein with an 18-amino-acid signal peptide with a consensus IIGG cleavage motif. The predicted protein encoded by milT is homologous to ABC (ATP-binding cassette) transporters of several bacteriocin systems and to proteins implicated in the signal-sequence-independent export of Escherichia coli hemolysin A. These similarities strongly suggest that the milT gene product is involved in the translocation of millericin B. The gene milF encodes a protein of 302 amino acids that shows similarities to the FemA and FemB proteins of Staphylococcus aureus, which are involved in the addition of glycine to a pentapeptide peptidoglycan precursor. Comparisons of the cell wall mucopeptide of S. milleri NMSCC 061(resistant to lysis by millericin B) and S. milleri NMSCC 051(sensitive) showed a single amino acid difference. Serial growth of S. milleri NMSCC 051 in a cell wall minimal medium containing an increased concentration of leucine resulted in the in vivo substitution of leucine for threonine in the mucopeptide of the cell wall. A cell wall variant of S. milleri NMSCC 051 (sensitive) that contained an amino acid substitution (leucine for threonine) within its peptidoglycan cross bridge showed partial susceptibility to millericin B. The putative tRNA(Leu) sequence located upstream of milB may be a cell wall-specific tRNA and could together with the milF protein, play a potential role in the addition of leucine to the pentapeptide peptidoglycan precursor and thereby, contributing to self-protection to millericin B in the producer strain.Keywords
This publication has 80 references indexed in Scilit:
- Characterization of the murMN Operon Involved in the Synthesis of Branched Peptidoglycan Peptides in Streptococcus pneumoniaePublished by Elsevier ,2000
- Zoocin A immunity factor: afemA-like gene found in a group C streptococcusFEMS Microbiology Letters, 1998
- A family of bacteriocin ABC transporters carry out proteolytic processing of their substrates concomitant with exportMolecular Microbiology, 1995
- Plasmid-encoded lysostaphin endopeptidase resistance of staphylococcussimulans biovar staphylolyticusBiochemical and Biophysical Research Communications, 1989
- The detection and classification of membrane-spanning proteinsBiochimica et Biophysica Acta (BBA) - Biomembranes, 1985
- Inhibition of bacterial wall lysins by lipoteichoic acids and related compoundsBiochemical and Biophysical Research Communications, 1975
- On the physiological functions of teichoic acidsJournal of Supramolecular Structure, 1975
- Effect of glycl-tRNA concentration on in vitro serine incorporation into the peptidoglycan of S. epidermidisBiochemical and Biophysical Research Communications, 1973
- Novel Species of tRNANature, 1971
- Structures of the cell wall peptidoglycans of Staphylococcus epidermidis Texas 26 and Staphylococcus aureus Copenhagen. II. Structure of neutral and basic peptides from hydrolysis with the Myxobacter Al-1 peptidaseBiochemistry, 1969