Crystallographic, Molecular Modeling, and Biophysical Characterization of the Valine67 (E11)
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- 作者：Igor Pechik ; Xinhua Ji ; Krzysztof Fidelis ; Michael Karavitis ; John Moult ; William S. Brinigar ; Clara Fronticelli ; and Gary L. Gilliland
- 刊名：Biochemistry
- 出版年：1996
- 出版时间：February 13, 1996
- 年：1996
- 卷：35
- 期：6
- 页码：1935 - 1945
- 全文大小：497K
- 年卷期：v.35,no.6(February 13, 1996)
- ISSN：1520-4995
文摘
The crystal structure of the mutant deoxyhemoglobin in which the
-globin Val67(E11) hasbeen replaced with threonine [Fronticelli et al. (1993)Biochemistry 32, 1235-1242] has beendeterminedat 2.2 Å resolution. Prior to the crystal structuredetermination, molecular modeling indicated that theThr67(E11) side chain hydroxyl group in the distal-heme pocket forms a hydrogen bond with the backbonecarbonyl of His63(E7) and is within hydrogen-bondingdistance of the N
of His63(E7).The mutant crystalstructure indicates only small changes in conformation in the vicinityof the E11 mutation confirming themolecular modeling predictions. Comparison of the structures ofthe mutant -subunits and recombinantporcine myoglobin with the identical mutation [Cameron et al. (1993)Biochemistry 32, 13061-13070]indicates similar conformations of residues in the distal heme pocket,but there is no water moleculeassociated with either of the threonines of the -subunits. Theintroduction of threonine into the distalheme pocket, despite having only small perturbations in the localstructure, has a marked affect on theinteraction with ligands. In the oxy derivative there is a 2-folddecrease in O2 affinity [Fronticelli et al.(1993) Biochemistry 32, 1235-1242], and therate of autoxidation is increased by 2 orders ofmagnitude.In the CO derivative the IR spectrum shows modifications withrespect to that of normal human hemoglobin,suggesting the presence of multiple CO conformers. In the nitrosylderivative an interaction with the O
atom of Thr67(E11) is probably responsible for the10-fold increase in the rate of NO release from the-subunits. In the aquomet derivative there is a 6-fold decreasein the rate of hemin dissociation suggestingan interaction of the Fe-coordinated water with the O ofThr67(E11).
-globin Val67(E11) hasbeen replaced with threonine [Fronticelli et al. (1993)Biochemistry 32, 1235-1242] has beendeterminedat 2.2 Å resolution. Prior to the crystal structuredetermination, molecular modeling indicated that theThr67(E11) side chain hydroxyl group in the distal-heme pocket forms a hydrogen bond with the backbonecarbonyl of His63(E7) and is within hydrogen-bondingdistance of the N of His63(E7).The mutant crystalstructure indicates only small changes in conformation in the vicinityof the E11 mutation confirming themolecular modeling predictions. Comparison of the structures ofthe mutant -subunits and recombinantporcine myoglobin with the identical mutation [Cameron et al. (1993)Biochemistry 32, 13061-13070]indicates similar conformations of residues in the distal heme pocket,but there is no water moleculeassociated with either of the threonines of the -subunits. Theintroduction of threonine into the distalheme pocket, despite having only small perturbations in the localstructure, has a marked affect on theinteraction with ligands. In the oxy derivative there is a 2-folddecrease in O2 affinity [Fronticelli et al.(1993) Biochemistry 32, 1235-1242], and therate of autoxidation is increased by 2 orders ofmagnitude.In the CO derivative the IR spectrum shows modifications withrespect to that of normal human hemoglobin,suggesting the presence of multiple CO conformers. In the nitrosylderivative an interaction with the Oatom of Thr67(E11) is probably responsible for the10-fold increase in the rate of NO release from the-subunits. In the aquomet derivative there is a 6-fold decreasein the rate of hemin dissociation suggestingan interaction of the Fe-coordinated water with the O ofThr67(E11).