期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 394, 期 1, 页码 143-159出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2009.09.037
关键词
Pseudomonas aeruginosa; type IV pili; PilO structure; PilN; Type II secretion
资金
- MOP [93585]
- Canadian Institutes of Health Research (CIHR)
- Canadian Cystic Fibrosis Foundation
- National Institutes of Health [U54 GM074945]
- U.S. Department of Energy
- Office of Science
- Office of Basic Energy Sciences [DE-AC02-06CH11357]
Type IV pili (TV) are bacterial virulence factors responsible for attachment to surfaces and for twitching motility, a motion that involves a succession of pilus extension and retraction cycles. In the opportunistic pathogen Pseudomonas aeruginosa, the PilM/N/O/P proteins are essential for TV biogenesis, and genetic and biochemical analyses strongly suggest that they form an inner-membrane complex. Here, we show through coexpression and biochemical analysis that the periplasmic domains of PilN and PilO interact to form a heterodimer. The structure of residues 69-201 of the periplasmic domain of PilO was determined to 2.2 angstrom resolution and reveals the presence of a homodimer in the asymmetric unit. Each monomer consists of two N-terminal coiled coils and a C-terminal ferredoxin-like domain. This structure was used to generate homology models of PilN and the PilN/O heterodimer. Our structural analysis suggests that in vivo PilN/O heterodimerization would require changes in the orientation of the first N-terminal coiled coil, which leads to two alternative models for the role of the transmembrane domains in the PilN/O interaction. Analysis of PilN/O orthologues in the type H secretion system EpsL/M revealed significant similarities in their secondary structures and the tertiary structures of PilO and EpsM, although the way these proteins interact to form inner-membrane complexes appears to be different in TV and type 11 secretion. Our analysis suggests that PilN interacts directly, via its N-terminal tail, with the cytoplasmic protein PilM. This work shows a direct interaction between the periplasmic domains of PilN and PilO, with PilO playing a key role in the proper folding of PilN. Our results suggest that PilN/O heterodimers form the foundation of the inner-membrane PilM/N/O/P complex, which is critical for the assembly of a functional TV complex. (C) 2009 Elsevier Ltd. All rights reserved.
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