EN
Methionyl-tRNA synthetase (MetRS) be longs to the fam ily of 20 en zymes es sen tial for pro tein biosynthesis. It links co va lently methionine with its cog nate tRNA. Crys tal structures solved for bac te rial MetRSs have given a num ber of in ter est ingin sights into en zyme ar chi tec ture and methionylation ca tal y sis. A com par i son of se quences of MetRSs be long ing to all king doms of life, as well as nu mer ous bio chem i cal and genetic stud ies have re vealed the pres ence of var i ous ad di tional do mains ap pended to the cat a lytic core of synthetase. They are re spon si ble for in ter ac tions with tRNA and pro teins. Ter tiary struc ture of C-terminal tRNA-binding ap pen di ces can be de duced from those de ter mined for their homo logues: tRNA bind ing pro tein 111 and en do the- lial monocyte-activating polypeptide II. Con tacts be tween MetRS and other pro teins could be me di ated not only by noncatalytic pep tides but also by struc tural el e ments pres ent in the cat a lytic core, e.g. Arg-Gly-Asp (RGD) mo tifs. Ad di tional ac tiv i ties involve MetRS in the main te nance of translational fi del ity and in co or di na tion of ri bo- some biogenesis with protein synthesis.