Probing the smallest functional unit of the reaction center of Rhodospirillum rubrum G‐9 with proteinases

Publisher Website
Google Scholar
Abstract
Reaction centers composed of subunits H, M, L (28 kDa, 24 kDa, 21 kDa) were isolated from Rhodospirillum rubrum G‐9 and subjected to progressive digestion with proteinase K. Photoactivity and spectral characteristics were retained as long as subunit L and a characteristic fragment (about 18 kDa) of another subunit, most probably of subunit M, remained intact. This was shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by the finding of only two amino‐terminal sequences one of which was identical with that of subunit L. The rate of reduction of photooxidized P‐870 was decreased in the digested preparation of the reaction center as compared with the control but the kinetics of the reduction of photooxidized cytochrome c 2 was unchanged. It is inferred that subunit L and a part of subunit M form the smallest functional unit of the reaction center.