Involvement of lysine 270 and lysine 271 of yeast 5S rRNA binding protein in RNA binding and ribosome assembly

摘要

Contributions of the highly conserved K270 and its neighboring K27I in the C-tenninal region of the yeast ribosomal protein LI to 5S rRNA binding and ribosome assembly were examined by in vivo and in vitro studies on the consequences of 14 substitution mutations. All mutant proteins with it single umino-ucid substitution ul either position were able to bind 5S rRNA in vitro to an extent comparable to the wild-type. Yeast cells expressing these mutant proteins, except the K270G mutant, grew at nearly normal rates. Mutations of K270 appeared to produce more demonstrable effects than those of K.271. The double mutant K270.27IG bound RNA poorly and yeast cells expressing the mutant protein grew 30% slower, Double mutants K27(),27lti and K270.271R were lethal, although the mutant protein was assembled into the 60S ribosomal summits. The resultant subunits were not stable leading eventually to cell death. The in vitro RNA liinding ability of the respective protein was reduced hy fi()% and 20%. Taken together, the present data identified K270 and K271 as important amino-acid residues in the function of the yeast ribosomal protein LI.