Protein Circlets as Sex Pilus Subunits

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

Journal Name: Current Protein & Peptide Science

Volume 5 , Issue 5 , 2004

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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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Article Details

VOLUME: 5
ISSUE: 5
Year: 2004
Page: [417 - 424]
Pages: 8
DOI: 10.2174/1389203043379639
Price: $58

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