Monoclonal antibodies referred to as Am1, Am2 and Am3 against highly purified bovine tryptophanyl‐tRNA synthetase were prepared. Am2 antibodies inhibit the Trp‐tRNA synthetase activity and interact with the active truncated enzyme forms (dimers of either 40‐kDa or 51‐kDa fragments) produced by limited proteolysis. Am1 and Am3 antibodies exert no effect on the Trp‐tRNA synthetase activity; epitopes recognized by them are mapped close to one another and reside at the dispensable part of the Trp‐tRNA synthetase molecule. Am1 cross‐reacts with Trp‐tRNA synthetases of eukaryotic, prokaryotic and archaebacterial species, as revealed by immunoblot analysis. A rapid two‐step technique was developed for isolating electrophoretically homogeneous Trp‐tRNA synthetase from Escherichia coli. The purified enzyme interacted with Am1, but not with Am2 and Am3 antibodies taken at the same concentrations. As in the case of eukaroytic Trp‐tRNA synthetase, Am1 did not influence the activity of Trp‐tRNA synthetase from E. coli. From the aforementioned results it follows that: (a) the conservation of part of the Trp‐tRNA synthetase structure which is not directly involved in the formation of the catalytic centre of prokaryotic and eukaryotic Trp‐tRNA synthetases suggests that the dispensalbe part of the molecule might be involved in some additional biological function(s) of Trp‐tRNA synthetase besides tRNATrp charging; (b) the common antigenic determinant in Trp‐tRNA synthetase of eukaryotes, prokaryotes and archaebacteria indicates that this enzyme was presumably present in the common ancestor of the above organisms.
|Original language||English (US)|
|Number of pages||7|
|Journal||European Journal of Biochemistry|
|State||Published - Oct 1989|
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