Limited proteolysis study of the structure of chloroplast coupling factor CF1
The structure of chloroplast coupling factor CF1 was studied by limited proteolysis followed by sodium dodecylsulfate polyacrylamide gel electrophoresis and N-terminal sequence analysis. The N-terminal fragment of the alpha-subunit was shown to have an exposed area including the peptide bonds E17--G18, R21--E22, E22--V23, and K24--V25. The cleavage of peptide bonds at amino acid residues E22 or/and V25 caused weaker subunit interactions and partial dissociation of the alpha- and gamma-subunits. In the N-terminal fragment of the isolated CF1 beta-subunit, the L14--E15 bond was found to be exposed to proteolytic attack. Also, the alphaS86--S87, alphaE125--S126, alphaR127--L128, and betaV76--A77 bonds were subject to proteolysis. The correlation between the accessibility of these bonds to proteases and the surface location of similar bonds in mitochondrial F1 was deduced from its molecular structure and a computed model of CF1. The K204--C205 bond exposed to protease on reduction of the CF1 gamma-subunit was shown to be masked when the catalytic reaction was initiated by CaATP.
Malyan
AN
Institute of Soil Science and Photosynthesis, Russian Academy of Sciences, Pushchino, Moscow Region, 142292, Russia. Malyan@issp. serpukhov.su.
Vitseva
OI
Gubanova
ON
Muranova
TA