RRM
2008 Rustbelt RNA Meeting
RRM
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Poster abstracts
Abstract:
Ribosomes are responsible for catalyzing protein synthesis in all cells. Assembly of the four rRNAs and 78 ribosomal proteins in eukaryotic ribosomes requires a large molecular machinery of ~200 proteins and dozens of RNAs. GTPases are one class of assembly factors that is conserved from bacteria to humans and of specific interest due to its potential regulatory role. Previous work has demonstrated that the essential GTPase Bms1 promotes assembly of a pre-40S ribosomal particle essential for rRNA processing (1). Here, we focus on the mechanism by which the GTPase activity within Bms1 is stimulated by an unusual intramolecular GTPase-activating (GAP) domain. We have devised an assay in which GTPase and GAP domains are provided on separate molecules to identify the GAP domain. This assay has identified a 150 amino acid region that provides GTPase stimulation in trans. Interestingly, this region includes at least two essential amino acids as well as a conserved phosphorylation site, which regulates the activity of Bms1 in vivo. We are currently testing the role of the essential amino acids for GTPase activation as well as other functions of Bms1. Additionally, our experiments indicate the GAP domain is more effective when provided in trans than in cis, indicating the alignment of the domains in the free Bms1 protein is not optimized. The signal that brings the two domains into contact will be probed to better understand and potentially block the contact leading to activation. Investigating the interaction of the domains will lead us to determine whether binding to pre-ribosomes influences the interaction between the GAP and GTPase domains of Bms1.
References:
1. Karbstein, K., Jonas, S., Doudna, J. (2005) An Essential GTPase Promotes Assembly of Preribosomal RNA Processing Complexes. Mol. Cell 20, 633-643.
Keywords: Small subunit assembly, GTPase, ribosome biogenesis
