Structure-function and biogenesis of the type IV pili.
Type IV pili are adhesins expressed by a number of diverse gram-negative microorganisms. These pili are related through similarities in the primary amino acid sequences of the structural subunits, a conserved assembly machinery, and a similar mechanism of transcriptional regulation. Type IV pilus assembly is preceded by proteolytic processing and N-methylation of the pilin polypeptide. This process is carried out by a novel bifunctional enzyme PilD, first identified in Pseudomonas aeruginosa. Moreover, proteins homologous with type IV pilins have been shown to function in extracellular protein secretion in gram-negative bacteria and in transformation competence in gram-positive microorganisms. Like prepilin, these proteins are also processed and N-methylated by PilD. Transcription of the genes for type IV pilins is carried out by an RNA polymerase with a minor sigma factor, RpoN. In P. aeruginosa two other regulatory elements (PilS and PilR) are required for pilin expression. RpoN, but not PilS and PilR, is required for expression of a diverse set of bacterial genes. Therefore, regulation of synthesis and posttranslational modification and assembly of type IV pili serves as a useful model for a number of diverse biological processes in the bacterial cell.
Strom
M S
MS
Department of Microbiology, University of Washington, Seattle 98195.
Lory
S
S
D000595:Amino Acid Sequence; D001419:Bacteria / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D010861:Fimbriae, Bacterial / Q000737:chemistry / Q000145:classification / Q000502:physiology*; D008969:Molecular Sequence Data; D013329:Structure-Activity Relationship