title: Comparative analysis of structural and dynamic properties of the loaded and unloaded hemophore HasA: functional implications.
abstract: A heme-acquisition system present in several Gram-negative bacteria requires the secretion of hemophores. These extracellular carrier proteins capture heme and deliver it to specific outer membrane receptors. The Serratia marcescens HasA hemophore is a monodomain protein that binds heme with a very high affinity. Its alpha/beta structure, as that of its binding pocket, has no common features with other iron- or heme-binding proteins. Heme is held by two loops L1 and L2 and coordinated to iron by an unusual ligand pair, H32/Y75. Two independent regions of the hemophore beta-sheet are involved in HasA-HasR receptor interaction. Here, we report the 3-D NMR structure of apoHasA and the backbone dynamics of both loaded and unloaded hemophore. While the overall structure of HasA is very similar in the apo and holo forms, the hemophore presents a transition from an open to a closed form upon ligand binding, through a large movement, of up to 30 A, of loop L1 bearing H32. Comparison of loaded and unloaded HasA dynamics on different time scales reveals striking flexibility changes in the binding pocket. We propose a mechanism by which these structural and dynamic features provide the dual function of heme binding and release to the HasR receptor.
authors.affiliation: Unité de RMN des Biomolécules, CNRS URA 2185, Département de Biologie Structurale et de Chimie, Institut Pasteur, 75724 Paris Cedex 15, France. wolff@pasteur.fr
authors.forename: Nicolas
authors.initials: N
authors.lastname: Wolff
authors.forename: Nadia
authors.initials: N
authors.lastname: Izadi-Pruneyre
authors.forename: Joël
authors.initials: J
authors.lastname: Couprie
authors.forename: Michael
authors.initials: M
authors.lastname: Habeck
authors.forename: Jens
authors.initials: J
authors.lastname: Linge
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Rieping
authors.forename: Cécile
authors.initials: C
authors.lastname: Wandersman
authors.forename: Michael
authors.initials: M
authors.lastname: Nilges
authors.forename: Muriel
authors.initials: M
authors.lastname: Delepierre
authors.forename: Anne
authors.initials: A
authors.lastname: Lecroisey
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; D008024:Ligands; D008027:Light; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012542:Scattering, Radiation; D012706:Serratia marcescens / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; C093956:HasA protein, Serratia marcescens; D000081062:Heme-Binding Proteins; D006420:Hemeproteins; D008024:Ligands; D008565:Membrane Proteins; D006418:Heme