Alteration of a 30S ribosomal protein accompanying the ram mutation in Escherichia coli.

The functional peculiarities of ram mutants correlate with an observed alteration in chromatographic mobility of P4(a), a specific protein of the 30S ribosomal subunit. This finding is supported by ribosomal reconstitution experiments. These facts, together with the known location of the ram mutational site in the vicinity of other 30S genetic determinants, suggest that ram is the structural gene for P4(a). The known contrasting roles of ram and strA in determining translational efficiency require that the function of P4(a) should be explained in relation to P10 (the 30S-subunit protein defined by strA). One consequence of altering P4(a), a key protein in ribosome assembly, might be to change the interaction of P10 with the 30S subunit. The functional interrelationship of P4(a) and P10 is discussed in terms of the possible roles of these two proteins in regulating access of tRNA molecules to the decoding site.