3sj5

I5F Mutant Structure of T. Tengcongensis H-NOX

spinqualitylabelsall models 3sj5, resolution 1.67Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3sj5 is a 2 chain structure with sequence from Caldanaerobacter subterraneus subsp. tengcongensis. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.673Å Ligands: HEM Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q8RBX6_CALS4 Publication Abstract from PubMed Heme Nitric oxide/OXygen binding (H-NOX) domains have provided a novel scaffold to probe ligand affinity in hemoproteins. Mutation of isoleucine 5, a conserved residue located in the heme-binding pocket of the H-NOX domain from Thermoanaerobacter tengcongensis (Tt H-NOX), was carried out to examine changes in oxygen (O(2))-binding properties. A series of I5 mutants (I5F, I5F/I75F, I5F/L144F, I5F/I75F/L144F) were investigated to probe the role of steric bulk within the heme pocket. The mutations significantly increased O(2) association rates (1.5-2.5-fold) and dissociation rates (8-190-fold) as compared to wild-type Tt H-NOX. Structural changes that accompanied the I5F mutation were characterized using X-ray crystallography and resonance Raman spectroscopy. A 1.67 A crystal structure of the I5F mutant indicated that introducing a phenylalanine at position 5 resulted in a significant shift of the N-terminal domain of the protein, causing an opening of the heme pocket. This movement also resulted in an increased amount of flexibility at the N-terminus and the loop covering the N-terminal helix as indicated by the two conformations of the first six N-terminal amino acids, high B-factors in this region of the protein, and partially discontinuous electron density. In addition, introduction of a phenylalanine at position 5 resulted in increased flexibility of the heme within the pocket and weakened hydrogen bonding to the bound O(2) as measured by resonance Raman spectroscopy. This study provides insight into the critical role of I5 in controlling conformational flexibility and ligand affinity in H-NOX proteins. Controlling Conformational Flexibility of an O(2)-Binding H-NOX Domain.,Weinert EE, Phillips-Piro CM, Tran R, Mathies RA, Marletta MA Biochemistry. 2011 Jul 15. PMID:21721586 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Chemotaxis protein 3D structures Methyl-accepting chemotaxis protein

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