2J0R

Structure of the haem-chaperone Proteobacteria-protein HemS

Summary for 2J0R

• Entry DOI: 10.2210/pdb2j0r/pdb
• Related: 2J0P
• Descriptor: HEMIN TRANSPORT PROTEIN HEMS, 1,2-ETHANEDIOL, DI(HYDROXYETHYL)ETHER, ... (7 entities in total)
• Functional Keywords: transport protein, proteobacteria, iron transport
• Biological source: YERSINIA ENTEROCOLITICA
• Total number of polymer chains: 1
• Total formula weight: 40808.68

Authors

Schneider, S.,Sharp, K.H.,Barker, P.D.,Paoli, M. (deposition date: 2006-08-04, release date: 2006-08-29, Last modification date: 2023-12-13)

Primary citation

Schneider, S.,Sharp, K.H.,Barker, P.D.,Paoli, M.
An Induced Fit Conformational Change Underlies the Binding Mechanism of the Heme Transport Proteobacteria-Protein Hems.
J.Biol.Chem., 281:32606-, 2006

PubMed Abstract: Bacteria rely on their environment and/or host to acquire iron and have evolved specialized systems to sequester and transport heme. The heme uptake system HemRSTUV is common to proteobacteria, and a major challenge is to understand the molecular mechanism of heme binding and transfer between the protein molecules that underlie this heme transport relay process. In the Gram-negative pathogen Yersinia enterocolitica, the HemRSTUV system culminates with the cytoplasmic recipient HemS, which stores and delivers heme for cellular needs. HemS belongs to a family of proteins essential and unique to proteobacteria. Here we report on the binding mechanism of HemS based on structural data from its apo- and ligand-loaded forms. This heme carrier protein associates with its cargo through a novel, partly preformed binding pocket, formed between a large beta-sheet dome and a three-helix subdomain. In addition to a histidine interacting with the iron, the complex is stabilized by a distal non-coordinating arginine that packs along the porphyrin plane and extensive electrostatic contacts that firmly anchor the heme propionate groups within the protein. Comparison of apo- and ligand-bound HemS crystal structures reveals striking conformational changes that underlie a "heme-induced fit" binding mechanism. Local shifts in amino acid positions combine with global, rigid body-like domain movements, and together, these bring about a switch from an open, apo-form to a closed, bound state. This is the first report in which both liganded and unliganded forms of a heme transport protein are described, thus providing penetrating insights into its mechanism of heme binding and release.

PubMed: 16943192
DOI: 10.1074/JBC.M607516200

Experimental method

X-RAY DIFFRACTION (1.9 Å)