Cold‐sensitive growth and decreased GTP‐hydrolytic activity from substitution of Pro17 for Val in Era, an essential Escherichia coli GTPase

A substitution mutation of Pro17 by Val (P17V) was constructed in the guanine nucleotide binding domain of Era, an essential protein in Escherichia coli. The mutation is analogous to the oncogenic activating allele at position 12 in the GTP‐binding domain of p21ras. The phenotype of this mutant was analysed in a strain which exclusively expressed the mutant protein (Era‐V17) in null allele chromosomal background (era1::kan). The strain was found to be cold‐sensitive for growth. Mutant Era‐V17 purified from the strain was cold‐sensitive for GTP‐hydrolytic activity, suggesting that the GTPase activity of Era is required for cell growth since the P17V mutation resulted in both cold‐sensitive growth of cells and cold‐labile GTPase activity of the purified protein.