An essential GTPase that binds both GDP and GTP, with nucleotide exchange occurring on the order of seconds whereas hydrolysis occurs on the order of minutes. Plays a role in numerous processes, including cell cycle regulation, energy metabolism, as a chaperone for 16S rRNA processing and 30S ribosomal subunit biogenesis. One of at least 4 proteins (Era, RbfA, RimM and RsgA/YjeQ) that assist in the late assembly stage of the 30S ribosomal subunit. Its presence in the 30S subunit may prevent translation initiation. Seems to be critical for maintaining cell growth and cell divison rates; a dramatic reduction in Era protein levels temporarily arrests cell growth just before cytokinesis (at the predivisional two-cell stage) and delays cell division. Era mutant era1 suppresses some temperature-sensitive mutations that affect DNA replication and chromosome partitioning and segregation. The dominant-negative Era-de mutant which is missing residues in a putative effector region, is unable to complement the disruption mutant; upon overproduction it shows a significant decrease in cell viability and a synthetic lethal phenotype in the presence of acetate. Era function probably overlaps RbfA (PubMed:16825789). Binds to the pre-30S ribosomal subunit through several stages of protein assembly (PubMed:20188109). GTPase is competitively inhibited by GDP but not by ADP, ATP, CTP or UTP. Monomer. Binds both 16S rRNA and 30S ribosomal subunits; binding is inhibited by GDP and GTP (PubMed:10094501). Bind preferentially to mature 30S ribosomal subunits over immature subunits in the presence of GMP-PNP (PubMed:27382067). Binds to MazG; GDP-bound Era binds more tightly to MazG than GTP-bound Era (PubMed:19706445). Binding is GDP or GTP-dependent, slightly more protein is bound in the presence of GTP than GDP. Expression increases as the growth rate increases. Encoded in the rnc-era-recO operon. Autophosphorylated. Lethality. In the presence of 1% protein cells grow extremely slowly and are blocked at the predivisional two-cell stage of the cell cycle. In the absence of Era and Rnc there is an additional defect in chromosome partitioning. In depletion experiments cells grow normally for 2 hours when protein levels fall. After 4 hours 16S rRNA levels decrease with a concomitant rise in the 17S precursor rRNA molecule (extra sequences at both the 5' and 3' end compared to mature 16S rRNA) and a loss of 70S ribosome assembly. When overexpressed partially suppresses the slow growth and decreased 70S ribosome phenotype of an rsgA knockout; RsgA may be involved in 30S ribosomal subunit biogenesis (PubMed:18223068). When overexpressed partially suppresses the 30S ribosomal subunit assembly defects and cold-sensitivity of an rbfA knockout; an era mutant missing residues 39-49 fully suppresses these phenotypes (PubMed:12753192). Overexpression is not able to suppress a rimM disruption phenotype nor a C23U mutation in 16S rRNA. Also suppresses temperature-sensitive mutations in DNA primase (PubMed:9093842). Belongs to the TRAFAC class TrmE-Era-EngA-EngB-Septin-like GTPase superfamily. Era GTPase family.