Abstract
Yeast tRNA-Phe has been cross-linked photochemically to three aminoacyl-tRNA synthetases, yeast phenylalanyl-tRNA synthetase, Escherichia coli isoleucyl-tRNA synthetase, and E. coli valyl-tRNA synthetase. The two non-cognate enzymes are known to interact with tRNA-Phe. In each complex, three regions on the tRNA are found to cross-link. Two of these are common to all of the complexes, while the third is unique to each. Thus, the cognate and non-cognate complexes bear considerable similarity to each other in the way in which the respective enzyme orients on tRNA-Phe, a result which was also established for the complexes of E. coli tRNA-Ile (BUDZIK, G.P., LAM, S.M., SCHOEMAKER, H.J.P., and SCHIMMEL, P.R. (1975) J. Biol. Chem. 250, 4433-4439). The common regions include a piece extending from the 5'-side of the acceptor stem to the beginning of the dihydrouridine helix, and a segment running from the 3' side of the extra loop into the TpsiC helix. These two regions overlap with and include some of the homologous bases found in eight tRNAs aminoacylated by yeast phenylalanyl-tRNA synthetase (ROE, B., SIROVER, M., and DUDOCK, B. (1973) Biochemistry 12, 4146-4153). Although well separated in the primary and secondary structure, these two segments are in close proximity in the crystallographic tertiary structure. In two of the complexes, the third cross-linked fragment is near to the two common ones. The picture which emerges is that the enzymes all interact with the general area in which the two helical branches of the L-shaped tertiary structure fuse together, with additional interactions on other parts of the tRNAas well.
Highlights
Yeast tRNAPhe has been photochemically joined to three aminoacyl-tRNA synthetases, yeast phenylalanyl-tRNA synthetase, Escherichia coli isoleucyl-tRNA synthetase, and E. coli valyl-tRNA synthetase. It is known from fluorescence titration studies that E. coli isoleucyl-tRNA synthetase forms a fairly strong complex with tRNA:,h,‘, [8], attempts to aminoacylate tRNA,P,h,‘, with E. coli isoleucyl-tRNA synthetase have failed under a variety of conditions.’
Valyl-tRNA synthetase and isoleucyl-tRNA synthetase were isolated from Escherichia coli by the procedures of Yaniv and Gros [12] and Eldred and Schimmel [13], respectively
It is immediately apparent from these figures that the two cross-linked fragments common to all three complexes, 10A and 12, spaced well apart in the primary and secondary structure are quite close in the tertiary structure (l-3)
Summary
Yeast tRNAPhe has been cross-linked photochemically to three aminoacyl-tRNA synthetases, yeast phenylalanyltRNA synthetase, Escherichia coli isoleucyl-tRNA synthetase, and E. coli valyl-tRNA synthetase. Yeast tRNAPhe has been photochemically joined to three aminoacyl-tRNA synthetases, yeast phenylalanyl-tRNA synthetase, Escherichia coli isoleucyl-tRNA synthetase, and E. coli valyl-tRNA synthetase It is known from fluorescence titration studies that E. coli isoleucyl-tRNA synthetase forms a fairly strong complex with tRNA:,h,‘,, [8], attempts to aminoacylate tRNA,P,h,‘,, with E. coli isoleucyl-tRNA synthetase have failed under a variety of conditions.’. E. coli valyl-tRNA synthetase is known to aminoacylate tRNAEc&,h,‘,w, ith valine [9, 10] Both noncognate enzymes show evidence for interaction with tRNAf,h,‘,,, and make good candidates with which to explore structurefunction aspects of non-cognate complexes and their relationship to the cognate one. The analysis of the structures of the three complexes gives considerably more input into the attempt to deduce a general picture, if any, for the way in which a synthetase orients on a tRNA
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
