CRYSTALLIZATION AND MICRO FT-IR SPECTROSCOPY INVESTIGATION OF CYTOCHROME BC(1) COMPLEX

A simple method to obtain large red crystals of cytochrome be, complex from beef heart mitochondria has been developed. These crystals are v ery stable. Their shapes are retained for a long time in tip-sealed Pa steur pipets placed in a refrigerator. The structure of crystalline cy tochrome bc(1) complex by micro FT-IR spectroscopy has been investigat ed. Based on the IR spectra of cytochrome c, the empirical assignments of the major infrared frequencies of cytochrome bc(1) complex are giv en. Infrared frequencies and relative intensities of variable orientat ion and section of crystal are significantly different. These imply th at infrared spectral characterization of the membrane protein crystall ization is associated with the variable symmetries and orientations of the structure. Experimental results show that phospholipid exists in the crystal of cytochrome bc(1) complex. The membrane protein is proba bly spanned on the mitochondrial membrane and buried in phospholipid b ilayer in an asymmetric manner.