3r9x
From Proteopedia
Crystal structure of Era in complex with MgGDPNP, nucleotides 1506-1542 of 16S ribosomal RNA, and KsgA
Structural highlights
Function[ERA_AQUAE] An essential GTPase that binds both GDP and GTP, with rapid nucleotide exchange. Plays a role in 16S rRNA processing and 30S ribosomal subunit biogenesis and possibly also in cell cycle regulation and energy metabolism (By similarity). The GTPase is stimulated about 6-fold in the presence of a 12 nucleotide 16S rRNA C-terminal fragment. Mutations in the rRNA sequence obviate stimulation. RNA-binding depends on GTP-binding by the GTPase domain. May function as a checkpoint for assembly of the 30S ribosomal subunit. [RSMA_AQUAE] Specifically dimethylates two adjacent adenosines (A1518 and A1519) in the loop of a conserved hairpin near the 3'-end of 16S rRNA in the 30S particle. May play a critical role in biogenesis of 30S subunits (By similarity). Publication Abstract from PubMedEra, composed of a GTPase domain and a K homology domain, is essential for bacterial cell viability. It is required for the maturation of 16S rRNA and assembly of the 30S ribosomal subunit. We showed previously that the protein recognizes nine nucleotides ( ) near the 3' end of 16S rRNA, and that this recognition stimulates GTP-hydrolyzing activity of Era. In all three kingdoms of life, the sequence and helix 45 (h45) (nucleotides 1506-1529) are highly conserved. It has been shown that the to double mutation severely affects the viability of bacteria. However, whether Era interacts with G1530 and/or h45 and whether such interactions (if any) contribute to the stimulation of Era's GTPase activity were not known. Here, we report two RNA structures that contain nucleotides 1506-1542 (RNA301), one in complex with Era and GDPNP (GNP), a nonhydrolysable GTP-analogue, and the other in complex with Era, GNP, and the KsgA methyltransferase. The structures show that Era recognizes 10 nucleotides, including G1530, and that Era also binds h45. Moreover, GTPase assay experiments show that G1530 does not stimulate Era's GTPase activity. Rather, A1531 and A1534 are most important for stimulation and h45 further contributes to the stimulation. Although G1530 does not contribute to the intrinsic GTPase activity of Era, its interaction with Era is important for binding and is essential for the protein to function, leading to the discovery of a new cold-sensitive phenotype of Era. The Era GTPase recognizes the GAUCACCUCC sequence and binds helix 45 near the 3' end of 16S rRNA.,Tu C, Zhou X, Tarasov SG, Tropea JE, Austin BP, Waugh DS, Court DL, Ji X Proc Natl Acad Sci U S A. 2011 Jun 6. PMID:21646538[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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