title: Mutational analysis of the ribosome assembly GTPase RbgA provides insight into ribosome interaction and ribosome-stimulated GTPase activation.
abstract: Ribosome biogenesis GTPase A protein (RbgA) is an essential GTPase required for the biogenesis of the 50S subunit in Bacillus subtilis. Homologs of RbgA are widely distributed in bacteria and eukaryotes and are implicated in ribosome assembly in the mitochondria, chloroplast and cytoplasm. Cells depleted of RbgA accumulate an immature large subunit that is missing key ribosomal proteins. RbgA, unlike many members of the Ras superfamily of GTPases, lacks a defined catalytic residue for carrying out guanosine triphosphate (GTP) hydrolysis. To probe RbgA function in ribosome assembly, we used a combined bioinformatics, genetic and biochemical approach. We identified a RNA-binding domain within the C-terminus of RbgA that is structurally similar to AmiR-NasR Transcription Anti-termination Regulator (ANTAR) domains, which are known to bind structured RNA. Mutation of key residues in the ANTAR domain altered RbgA association with the ribosome. We identified a putative catalytic residue within a highly conserved region of RbgA, His9, which is contained within a similar PGH motif found in elongation factor Tu (EF-Tu) that is required for GTP hydrolysis on interaction with the ribosome. Finally, our results support a model in which the GTPase activity of RbgA directly participates in the maturation of the large subunit rather than solely promoting dissociation of RbgA from the 50S subunit.
authors: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48823, USA.
authors: Megha
authors: M
authors: Gulati
authors: Nikhil
authors: N
authors: Jain
authors: Baskaran
authors: B
authors: Anand
authors: Balaji
authors: B
authors: Prakash
authors: Robert A
authors: RA
authors: Britton
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites; D017124:Conserved Sequence; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006150:Guanine Nucleotides / Q000737:chemistry; D006868:Hydrolysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D054681:Ribosome Subunits, Large, Bacterial / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D006150:Guanine Nucleotides; D012269:Ribosomal Proteins; D020558:GTP Phosphohydrolases