Heme uptake across the outer membrane as revealed by crystal structures of the receptor-hemophore complex.

Stefanie Krieg (1) , Frédéric Huché (1, 2, 3) , Kay Diederichs (1) , Nadia Izadi-Pruneyre (4) , Anne Lecroisey (4) , Cécile Wandersman (2) , Philippe Delepelaire (2) , Wolfram Welte (1)

1 Fachbereich Biologie
2 Membranes bactériennes
3 IBCP - Institut de biologie et chimie des protéines [Lyon]
4 Résonance Magnétique Nucléaire des Biomolécules

Gram-negative bacteria use specific heme uptake systems, relying on outer membrane receptors and excreted heme-binding proteins (hemophores) to scavenge and actively transport heme. To unravel the unknown molecular details involved, we present 3 structures of the Serratia marcescens receptor HasR in complex with its hemophore HasA. The transfer of heme over a distance of 9 A from its high-affinity site in HasA into a site of lower affinity in HasR is coupled with the exergonic complex formation of the 2 proteins. Upon docking to the receptor, 1 of the 2 axial heme coordinations of the hemophore is initially broken, but the position and orientation of the heme is preserved. Subsequently, steric displacement of heme by a receptor residue ruptures the other axial coordination, leading to heme transfer into the receptor.

Domains: Microbiology and Parasitology

Stefanie Krieg, Frédéric Huché, Kay Diederichs, Nadia Izadi-Pruneyre, Anne Lecroisey, et al.. Heme uptake across the outer membrane as revealed by crystal structures of the receptor-hemophore complex.. Proceedings of the National Academy of Sciences of the United States of America, 2009, 106 (4), pp.1045-50. ⟨10.1073/pnas.0809406106⟩. ⟨pasteur-00366353⟩