Cited by 2k
Novartis (Switzerland)
Publishes on Photosynthetic Processes and Mechanisms, Monoclonal and Polyclonal Antibodies Research, RNA and protein synthesis mechanisms. 58 papers and 5.1k citations.
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The aa3 type cytochrome c oxidase consisting of the core subunits I and II only was isolated from the soil bacterium Paracoccus denitrificans and crystallized as complex with a monoclonal antibody Fv fragment. Crystals could be grown in the presence of a number of different nonionic detergents. However, only undecyl-beta-D-maltoside and cyclohexyl-hexyl-beta-D-maltoside yielded well-ordered crystals suitable for high resolution x-ray crystallographic studies. The crystals belong to space group P212121 and diffract x-rays to at least 2.5 A (1 A = 0.1 nm) resolution using synchrotron radiation. The structure was determined to a resolution of 2.7 A using molecular replacement and refined to a crystallographic R-factor of 20.5% (Rfree = 25.9%). The refined model includes subunits I and II and the 2 chains of the Fv fragment, 2 heme A molecules, 3 copper atoms, and 1 Mg/Mn atom, a new metal (Ca) binding site, 52 tentatively identified water molecules, and 9 detergent molecules. Only four of the water molecules are located in the cytoplasmic half of cytochrome c oxidase. Most of them are near the interface of subunits I and II. Several waters form a hydrogen-bonded cluster, including the heme propionates and the Mg/Mn binding site. The Fv fragment binds to the periplasmic polar domain of subunit II and is critically involved in the formation of the crystal lattice. The crystallization procedure is well reproducible and will allow for the analysis of the structures of mechanistically interesting mutant cytochrome c oxidases.
Five new membrane protein structures have been determined since 1995 using X-ray crystallography: bacterial light-harvesting complex; bacterial and mitochondrial cytochrome c oxidases; mitochondrial bc1 complex; and alpha-hemolysin. These successes are partly based on advances in the crystallization procedures for integral membrane proteins. Variation of the size of the detergent micelle and/or increasing the size of the polar surface of the membrane protein is the most important route to well-ordered membrane protein crystals. The use of bicontinuous lipidic cubic phases also appears to be promising.