Biomaterial Database

The side-on copper(I) nitrosyl geometry in copper nitrite reductase is due to steric interactions with isoleucine-257. 2009

Anna C Merkle, and Nicolai Lehnert

Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, USA.

Density functional theory calculations were used to investigate the binding mode of copper(I) nitrosyl (Cu(I)-NO) in copper nitrite reductase (CuNIR). The end-on Cu(I)-NO geometry (2) was found to be the global energy minimum, while the side-on binding mode (1) corresponds to a local minimum. Isoleucine-257 severely interacts sterically with the Cu(I)-NO unit when bound end-on but not in the side-on case. In addition, the side-on geometry is also stabilized by a hydrogen bond between aspartic acid-98 and NO, estimated to be approximately 3 kcal/mol. The steric constraint of the CuNIR active site is mainly responsible for the observed side-on coordination of NO in the CuNIR crystal structure. We speculate that a small conformational change of the active site that slightly changes the position of isoleucine-257 would allow NO to bind end-on. This explains the observed end-on binding of NO to copper(I) when CuNIR is in solution.

UI	MeSH Term	Description	Entries
D007532	Isoleucine	An essential branched-chain aliphatic amino acid found in many proteins. It is an isomer of LEUCINE. It is important in hemoglobin synthesis and regulation of blood sugar and energy levels.	Alloisoleucine,Isoleucine, L-Isomer,L-Isoleucine,Isoleucine, L Isomer,L-Isomer Isoleucine
D008956	Models, Chemical	Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.	Chemical Models,Chemical Model,Model, Chemical
D008958	Models, Molecular	Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.	Molecular Models,Model, Molecular,Molecular Model
D009572	Nitrite Reductases	A group of enzymes that oxidize diverse nitrogenous substances to yield nitrite. (Enzyme Nomenclature, 1992) EC 1.	Nitrite Reductase,Reductase, Nitrite,Reductases, Nitrite
D009603	Nitroso Compounds	Organic compounds containing the nitroso (-N	Compounds, Nitroso
D003300	Copper	A heavy metal trace element with the atomic symbol Cu, atomic number 29, and atomic weight 63.55.	Copper-63,Copper 63
D013237	Stereoisomerism	The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)	Molecular Stereochemistry,Stereoisomers,Stereochemistry, Molecular,Stereoisomer
D018360	Crystallography, X-Ray	The study of crystal structure using X-RAY DIFFRACTION techniques. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	X-Ray Crystallography,Crystallography, X Ray,Crystallography, Xray,X Ray Crystallography,Xray Crystallography,Crystallographies, X Ray,X Ray Crystallographies