Table 1.

Characteristics of GTPases described in this review

GTPase	Crystal structure reference(s)	Molecular mass of E. coli homolog (kDa)	Major process(es) involved	Phylogenetic distribution(s)a	Essentialb	Cellular localization
MnmE	178, 228	49.3	tRNA modification	B, E*	+/−	Cytoplasmic, partially membrane associated
Era	47	33.9	Cell cycle regulation, assembly and maturation of 30S ribosomal subunit, energy metabolism	B, E	+/−	Cytoplasmic, partially membrane associated
Der	214	55.1	Cell cycle regulation, assembly and maturation of 50S ribosomal subunit	B, E	Yes	Cytoplasmic, partially membrane associated
YihA	64, 216	23.7	Cell cycle regulation, assembly and maturation of 50S ribosomal subunit	B, E, A	+/−	Cytoplasmic
Obg	34, 144	43.4	Cell cycle regulation, assembly and maturation of 50S ribosomal subunit, stringent response, stress response, morphological development, sporulation	B, E	Yes	Cytoplasmic, possibly partially membrane associated
YchF	251	39.8	Translation, stress response in plants, antioxidant response in humans	B, E, A	No	Cytoplasmic
HflX	276	48.4	Assembly and maturation of 50S ribosomal subunit	B, E, A	No	Cytoplasmic, partially membrane associated
IF-2	215	97.5	Assembly of the translation initiation complex	B, E, A	Yes	Cytoplasmic
EF-Tu	1	43.4	Delivery of aminoacyl-tRNAs to the ribosome	B, E, A	Yes	Cytoplasmic
EF-G	1	77.7	Ribosomal translocation	B, E, A	Yes	Cytoplasmic
LepA	79	66.7	Ribosomal back-translocation	B, E*	No	Cytoplasmic
Ffh	84, 134	49.9	Cotranslational targeting of membrane-bound proteins	B, E, A	Yes	Cytoplasmic
FtsY	185, 186	54.6	Membrane-bound signal recognition particle receptor	B, E, A	Yes	Cytoplasmic, partially membrane associated

^aB, bacteria; E, eukaryotes; E*, eukaryotic organelles of prokaryotic origin; A, archaea.

^b+/−, essential in certain genetic backgrounds or strains.