1wvp

From Proteopedia

proteopedia linkproteopedia link

spinqualitylabelsall models 1wvp, resolution 1.53Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Structure of chemically modified myoglobin with distal N-tetrazolyl-histidine E7(64)

Overview

Tetrazole-myoglobin (Tet-Mb), a site selectively modified myoglobin with, tetrazole anion (-CN4-) covalently attached to the imidazole N epsilon of, the distal histidine 64(E7) (see Fig. 1; Kamiya, N., Shiro, Y., Iwata, T., Iizuka, T., and Iwasaki, H. (1991) J. Am. Chem. Soc. 113, 1826-1829), exhibited unique properties in the reduction from ferric to ferrous states, and in the reaction of its deoxy form with O2. The redox potential of, Tet-Mb is obtained to be -193 mV, which is much lower than that of, unmodified (native) myoglobin (50 mV), possibly due to the electrostatic, interaction between the heme iron and the tetrazole group. The ferrous, deoxy form of Tet-Mb was rapidly oxidized to its ferric form in the, reaction with O2 at room temperature through an intermediary formation of, its oxy form and with the generation of O2-. The oxy form of Tet-Mb can be, detected by the optical spectral measurement at -12 degrees C, the rapid, scan measurement at room temperature, and the electron spin resonance, measurement of its cobalt-substituted derivative (Tet-Mb(Co2+)) at 77 K., In the kinetic measurement of the O2 binding reaction to Tet-Mb, its, association and dissociation rate constants in the bimolecular reaction, were 6.1 x 10(7) M-1 s-1 and 2200 s-1, respectively, showing that the, tetrazole modification of His-64 extremely accelerates its association and, dissociation rates. Taken together with the extremely fast autoxidation, rate (53 h-1) obtained, these kinetic results suggested that the channel, of O2 from the solvent region to the protein interior is open enough to, pass the external ligand. The structure is discussed in relation to those, of some genetic mutants. Taking these properties, we demonstrated that, Tet-Mb can catalyze O2 consumption to generate O2-, coupled with the, NADH-supported enzymatic reduction system of cytochrome P-450cam under an, aerobic condition.

About this Structure

1WVP is a Single protein structure of sequence from Physeter catodon with SO4 and HEM as ligands. Full crystallographic information is available from OCA.

Reference

Specific modification of structure and property of myoglobin by the formation of tetrazolylhistidine 64(E7). Reaction of the modified myoglobin with molecular oxygen., Shiro Y, Iwata T, Makino R, Fujii M, Isogai Y, Iizuka T, J Biol Chem. 1993 Sep 25;268(27):19983-90. PMID:8397193

Page seeded by OCA on Wed Nov 21 05:42:20 2007