Analysis of magnesium, europium and lead binding sites in methionine initiator and elongator tRNAs by specific metal‐ion‐induced cleavages

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Abstract
The specificity of cleavages in yeast and lupin initiator and elongator methionine tRNAs induced by magnesium, europium and lead has been analysed and compared with known patterns of yeast tRNAPhe hydrolysis. The strong D‐loop cleavages occur in methionine elongator tRNAs at similar positions and with comparable efficiency to those found in tRNAPhe, while the sites of weak anticodon loop cuts, identical in methionine elongator tRNAs, differ from those found in tRNAPhe. Methionine initiator tRNAs differ from their elongator counterparts: (a) they are cleaved in the D‐loop with much lower efficiency; (b) they are cleaved in the variable loop which is completely resistant to hydrolysis in elongator tRNAs; (c) cleavages in the anticodon loop are stronger in initiator tRNAs and they are located mostly at the 5′ side of the loop whereas in elongator tRNAs they occur mostly at the opposite, 3′ side of the loop. The distinct pattern of the anticodon loop cleavages is considered to be related to different conformations of the anticodon loop in the two types of methionine tRNAs.