Antibodies to the F1‐ATPase of Rhodospirillum rubrum and Its Purified Native β‐Subunit:

Abstract
Antibodies prepared against the R. rubrum F1-ATPase (RrF1) and its purified, native .beta.-subunit, exhibited cross-reactivity with the following soluble preparations of R. rubrum ATPase: RrF0 .cntdot. F1, RrF1 and the .beta.-subunit. Anti-RrF1, but not anti-.beta. antibodies, also formed precipitin lines with soluble .beta.-less RrF1, indicating that antigenic determinants of both the .beta.-subunit and the other 4 RrF1-subunits are expressed in the whole RrF1 molecule. Both antibodies agglutinated the R. rubrum chromatophores, suggesting that the .beta.-subunit is located on the external part of RrF1. Both antibodies inhibited ATP synthesis and hydrolysis activities of R. rubrum chromatophores, as well as all the soluble ATPase reactions. Similar concentrations of each antibody were required for 50% inhibition of all these reactions, but anti-RrF1 was always somewhat more effective than anti-.beta.. The .beta.-subunit is apparently involved in the catalytic site of the RrF1-enzyme. The antibodies prepared against R. rubrum F1-ATPase and its .beta.-subunit could bind the soluble lettuce chloroplast F1-ATPase (CF1) and inhibited ATP-linked reactions carried out by chloroplasts and by soluble CF1. In these reactions, unlike in the R. rubrum ones, anti-.beta. was a more potent inhibitor than the anti-RrF1 antibody. The cross-reaction obtained between the antibodies raised against R. rubrum F1 and its .beta.-subunit and the chloroplast CF1 indicates the presence of similar antigenic determinants in the photosynthetic prokaryotic and eukaryotic F1-ATPases, which have been conserved during evolution.

This publication has 41 references indexed in Scilit: