involved in binding of mRNA to ribosomes; m1-s1 refers to mutant shorter form; SS1 from Streptomyces aureofaciens has same mobility as S1 from E coli in Na dodecyl sulfate/polyacrylamide gel; RPS1A is wheat mitochondrial RPS1, a shortened homolog of the E coli protein; GenBank X69205 (RPS1A)