2gnv

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Revision as of 11:24, 8 November 2007

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spinqualitylabelsall models 2gnv, resolution 2.300Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal structure of non-symbiotic plant hemoglobin from rice, B10 mutant F40L

Overview

All plants contain an unusual class of hemoglobins that display, bis-histidyl coordination yet are able to bind exogenous ligands such as, oxygen. Structurally homologous hexacoordinate hemoglobins (hxHbs) are, also found in animals (neuroglobin and cytoglobin) and some cyanobacteria, where they are thought to play a role in free radical scavenging or ligand, sensing. The plant hxHbs can be distinguished from the others because they, are only weakly hexcacoordinate in the ferrous state, yet no structural, mechanism for regulating hexacoordination has been articulated to account, for this behavior. Plant hxHbs contain a conserved Phe at position B10, (Phe(B10)), which is near the reversibly coordinated distal His(E7). We, have investigated the effects of Phe(B10) mutation on kinetic and, equilibrium constants for hexacoordination and exogenous ligand binding in, the ferrous and ferric oxidation states. Kinetic and equilibrium constants, for hexacoordination and ligand binding along with CO-FTIR spectroscopy, midpoint reduction potentials, and the crystal structures of two key, mutant proteins (F40W and F40L) reveal that Phe(B10) is an important, regulatory element in hexacoordination. We show that Phe at this position, is the only amino acid that facilitates stable oxygen binding to the, ferrous Hb and the only one that promotes ligand binding in the ferric, oxidation states. This work presents a structural mechanism for regulating, reversible intramolecular coordination in plant hxHbs.

About this Structure

2GNV is a Single protein structure of sequence from Oryza sativa with HEM and DIO as ligands. Full crystallographic information is available from OCA.

Reference

Role of phenylalanine B10 in plant nonsymbiotic hemoglobins., Smagghe BJ, Kundu S, Hoy JA, Halder P, Weiland TR, Savage A, Venugopal A, Goodman M, Premer S, Hargrove MS, Biochemistry. 2006 Aug 15;45(32):9735-45. PMID:16893175

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