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Relevance of histidine‐84 in the elongation factor Tu GTPase activity and in poly(Phe) synthesis: Its substitution by glutamine and alanine
Author(s) -
Scarano Giuliana,
Krab Ivo M.,
Bocchini Vincenzo,
Parmeggiani Andrea
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00469-p
Subject(s) - gtpase , gtp' , ef tu , ribosome , elongation factor , stereochemistry , biochemistry , chemistry , protein biosynthesis , alanine , histidine , biology , amino acid , enzyme , rna , gene
Substitution of His‐84 (→ Gln and → Ala), a residue of the switch II region of E. coli elongation factor (EF) Tu, hardly affected the binding of GTP or GDP. The activity in poly(Phe) synthesis and GTP hydrolysis of EF‐Tu H84Q were both reduced to about 35%, as compared to EF‐Tu wt, whereas EF‐Tu H84A was inactive in poly(Phe) synthesis but still showed a 10% residual GTPase activity. Phe‐tRNA Phe exerted a similar inhibitory effect on the GTPase activity of EF‐Tu wt and EF‐Tu H84Q while abolishing that of EF‐Tu H84A. Ribosomes enhanced the GTPase activity of EF‐Tu H84Q, but not that of EF‐Tu H84A, on which they even seemed to exert an inhibitory effect. The one‐round GTP hydrolysis associated with the EF‐TuH84Q‐dependent binding of Phe‐tRNA Phe to poly(U)‐programmed ribosomes was less efficient than with EF‐Tu wt. Kirromycin stimulated the GTPase activities of both mutants less than EF‐Tu wt. The results of this work do not support a catalytic role of His‐84 in the intrinsic GTPase of EF‐Tu, but they emphasize the importance of its side‐chain for polypeptide synthesis and GTP hydrolysis.