A new crystal form of bovine heart ubiquinol: cytochromecoxidoreductase: determination of space group and unit-cell parameters

Abstract

Ubiquinol:cytochrome c oxidoreductase, the middle segment of the mitochondrial respiratory chain, is a multi-subunit transmembrane redox enzyme. The purified protein from beef heart mitochondria has been crystallized by three groups in three different forms, but progress toward a structure has been hampered by the limited order (resolution) of the crystals. It has been found that under certain conditions the enzyme crystallizes in a new form suitable for X-ray diffraction studies. These crystals belong to space group C222(1) in the orthorhombic system. The cell dimensions are a = 384, b = 118 and c = 177 A. These new crystals at present diffract to 3.8 A at best. This is not significantly better than hexagonal [P6(1(5))22] crystals grown, but the new crystals have the advantage of less spot overlap because of face-centered packing which results in systematic extinctions. More importantly, the availability of the same enzyme in multiple crystal forms may allow phase refinement and extension by the method of molecular replacement.

Rationalization of Membrane Protein Crystallization with Polyethylene Glycol Using a Simple Depletion Model

“…BC1 was crystallized for the first time by two groups (Yue et al, 1991;Kubota et al, 1991) using PEG4000 as a main crystallization agent. Then crystal quality was improved, but still PEG4000 was mainly used (Kawamoto et al, 1994;Berry et al 1995;Lee et al, 1995). The molecular weight of 4000 that was empirically chosen was reasonable for BC1 as discussed above.…”

Structural basis for the mechanism of electron bifurcation at the quinol oxidation site of the cytochrome bc 1 complex

“…These studies revealed that the bovine bc 1 is dimeric with its molecular mass unevenly distributed about the two sides of the membrane. Crystallizations of mitochondrial bc 1 were reported as early as 1991 (Yue et al 1991) and extensive efforts were made by a number of research groups around the world (Berry et al 1992;Yu and Yu 1993;Berry et al 1995;Yu et al 1996;Lee et al 1995), contributing to the final structural solutions of this important complex in various crystal forms. The first bc 1 structure was published nearly ten years ago (Xia et al 1997) for the bovine complex (Fig.…”

Structure and Function of CytochromebcComplexes

“…Two new crystal forms were reported in 1995 (90). The initial needle crystals were improved in size and shape to give uniform or tapered hexagonal rods.…”

“…They belonged to the space group P6 1 22 or P6 5 22. They diffracted to 4.6Å using synchrotron radiation recorded on X-ray film, and 3.8Å with imaging plate detector (90).…”