Lability of the terminal 3′-hydroxy sequence of transfer RNA in microorganisms. II. Turnover of terminal AMP in Escherichia coli as a function of growth rate The turnover rate of t-RNA terminal AMP has been measured in Escherichia coli ML 308 as a function of the growth rate, using [8- 14C]adenine as a marker and alkaline degradation of labelled t-RNA to obtain terminal adenosine and internal AMP separately. Terminal adenosine turnover is too slow a phenomenon to be the direct consequence of amino acid transfer into peptide linkages. The turnover rate, expressed as per cent of the total terminal adenosine per min, increases with the growth rate; the turnover per generation, expressed as per cent of the average total adenosine per generation, remains constant at all growth rates examined. These results are discussed in terms of a possible mechanism accounting for terminal AMP renewal.