Cold-sensitive conditional mutations in Era, an essential Escherichia coli GTPase, isolated by localized random...

Conditional cold-sensitive mutations in Era, an essential Escherichia coli GTPase, were isolated. Localized random polymerase chain reaction (PCR) mutagenesis employing Taq and T7 DNA polymerases under error prone amplification conditions was exploited to generate mutations in the era gene. A plasmid exchange technique was used to identify conditional cold-sensitive mutations in Era that give rise to defective cell growth below 30 degrees C. Three recessive missense mutations in Era, N26S, A156D, and E200K, were isolated. All three mutations are located at residues conserved in Era homologues from Streptococcus mutans and Coxiella burnetti.