Crystal structure of ERA: a GTPase-dependent cell cycle regulator containing an RNA binding motif.
ERA forms a unique family of GTPase. It is widely conserved and essential in bacteria. ERA functions in cell cycle control by coupling cell division with growth rate. ERA homologues also are found in eukaryotes. Here we report the crystal structure of ERA from Escherichia coli. The structure has been determined at 2.4-A resolution. It reveals a two-domain arrangement of the molecule: an N-terminal domain that resembles p21 Ras and a C-terminal domain that is unique. Structure-based topological search of the C domain fails to reveal any meaningful match, although sequence analysis suggests that it contains a KH domain. KH domains are RNA binding motifs that usually occur in tandem repeats and exhibit low sequence similarity except for the well-conserved segment VIGxxGxxIK. We have identified a betaalphaalphabeta fold that contains the VIGxxGxxIK sequence and is shared by the C domain of ERA and the KH domain. We propose that this betaalphaalphabeta fold is the RNA binding motif, the minimum structural requirement for RNA binding. ERA dimerizes in crystal. The dimer formation involves a significantly distorted switch II region, which may shed light on how ERA protein regulates downstream events.
Biomolecular Structure Group, Advanced BioScience Laboratories-Basic Research Program, National Cancer Institute-Frederick Cancer Research and Development Center, P.O. Box B, Frederick, MD 21702, USA.
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D001426:Bacterial Proteins / Q000737:chemistry; D001665:Binding Sites; D002453:Cell Cycle; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins; D051860:Fragile X Messenger Ribonucleoprotein 1; D020558:GTP Phosphohydrolases / Q000737:chemistry*; D019204:GTP-Binding Proteins / Q000737:chemistry*; D006860:Hydrogen Bonding; D008565:Membrane Proteins / Q000737:chemistry; D008958:Models, Molecular; D009419:Nerve Tissue Proteins; D017510:Protein Folding; D017433:Protein Structure, Secondary; D016601:RNA-Binding Proteins / Q000737:chemistry; D018631:ras Proteins / Q000737:chemistry
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D051860:Fragile X Messenger Ribonucleoprotein 1; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D018631:ras Proteins; C068027:era protein, E coli