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Current Protein & Peptide Science

Editor-in-Chief

ISSN (Print): 1389-2037
ISSN (Online): 1875-5550

Protein Circlets as Sex Pilus Subunits

Author(s): Markus Kalkum, Ralf Eisenbrandt and Erich Lanka

Volume 5, Issue 5, 2004

Page: [417 - 424] Pages: 8

DOI: 10.2174/1389203043379639

Price: $65

Abstract

The largest circular protein structures discovered define a class of transfer proteins acting in bacterial conjugation and type IV secretion. Proteins ranging from 73 to 78 residues with head-to-tail peptide bonds constitute the major subunit of conjugative pili of some type IV secretion systems. Their plasmid-encoded precursors are enzymatically processed and cyclized before being assembled into pili. These extra-cellular surface filaments mediate physical contact between donor and recipient cell or pathogen and host cell. Pili are essential prerequisites for DNA and protein transfer. A membrane-bound signal peptidase-like enzyme is responsible for the circularization reaction. Site-directed mutagenesis and mass spectrometry has been used extensively to unravel the mechanism of the enzyme-substrate interaction of the pilin maturation process.

Keywords: protein circlets, sex pilus subunits, type IV secretion systems, enzyme-substrate interaction


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