Proteolysis of truncated hemolysin A yields a stable dimerization interface.

ABSTRACT: Wild-type and variant forms of HpmA265 (truncated hemolysin A) from Proteus mirabilis reveal a right-handed, parallel ?-helix capped and flanked by segments of antiparallel ?-strands. The low-salt crystal structures form a dimeric structure via the implementation of on-edge main-chain hydrogen bonds donated by residues 243-263 of adjacent monomers. Surprisingly, in the high-salt structures of two variants, Y134A and Q125A-Y134A, a new dimeric interface is formed via main-chain hydrogen bonds donated by residues 203-215 of adjacent monomers, and a previously unobserved tetramer is formed. In addition, an eight-stranded antiparallel ?-sheet is formed from the flap regions of crystallographically related monomers in the high-salt structures. This new interface is possible owing to additional proteolysis of these variants after Tyr240. The interface formed in the high-salt crystal forms of hemolysin A variants may mimic the on-edge ?-strand positioning used in template-assisted hemolytic activity.

SUBMITTER: Novak WR 

PROVIDER: S-EPMC5349307 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature