3aeh
Integral membrane domain of autotransporter Hbp
Structural highlights
FunctionHBP_ECOLX Interacts with hemoglobin, degrades it and subsequently binds the released heme. Could make heme accessible not only for E.coli, but also for B.fragilis during mixed intra-abdominal infections. Has a role in abscess formation.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMany virulence factors secreted by pathogenic Gram-negative bacteria are found to be members of the autotransporter protein family. These proteins share a common mechanism by which they exit the periplasm, involving the formation of a 12-stranded beta-barrel domain in the outer membrane. The role of this barrel in the secretion of the N-terminal passenger domain is controversial, and no model currently explains satisfactorily the entire body of experimental data. After secretion, some autotransporter barrels autoproteolytically cleave away the passenger, and one crystal structure is known for a barrel of this type in the postcleavage state. Hbp is an autotransporter of the self-cleaving type, which cuts the polypeptide between two absolutely conserved asparagine residues buried within the barrel lumen. Mutation of the first asparagine residue to isosteric aspartic acid prevents proteolysis. Here we present the crystal structure of a truncated Hbp mutant carrying the C-terminal residues of the passenger domain attached to the barrel. This model mimics the state of the protein immediately prior to separation of the passenger and barrel domains, and shows the role of residues in the so-called "linker" between the passenger and beta domains. This high-resolution membrane protein crystal structure also reveals the sites of many water molecules within the barrel. The cleavage mechanism shows similarities to those of inteins and some viral proteins, but with a novel means of promoting nucleophilic attack. A novel intein-like autoproteolytic mechanism in autotransporter proteins.,Tajima N, Kawai F, Park SY, Tame JR J Mol Biol. 2010 Oct 1;402(4):645-56. Epub 2010 Jul 6. PMID:20615416[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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