ABSTRACT
Eukaryotic and archaeal translation initiation factor 2 in complex with GTP delivers the initiator methionyl-tRNA to the small ribosomal subunit. Over the past 20 years, thanks to the efforts of various research groups, including ours, this factor from the archaeon Sulfolobus solfataricus and its individual subunits have been crystallized in ten different space groups. Analysis of the molecular packing in these crystals makes it possible to better understand the roles of functionally significant switches and other elements of the nucleotide-binding pocket during the function of the factor as well as the influence of external effects on its transition between active and inactive states.
Subject(s)
Archaeal Proteins , Sulfolobus solfataricus , Sulfolobus solfataricus/chemistry , Sulfolobus solfataricus/metabolism , Archaeal Proteins/chemistry , Archaeal Proteins/metabolism , Crystallography, X-Ray , Models, Molecular , Guanosine Triphosphate/metabolism , Guanosine Triphosphate/chemistry , Peptide Initiation Factors/chemistry , Peptide Initiation Factors/metabolism , Protein Conformation , Binding Sites , RNA, Transfer, Met/chemistry , RNA, Transfer, Met/metabolismABSTRACT
Aminoacyl-tRNA synthetases are an ancient enzyme family that specifically charge a tRNA molecule with a cognate amino acid required for protein synthesis. Glycyl-tRNA synthetase is one of the most interesting aminoacyl-tRNA synthetases due to its structure variability and functional features in the different organisms. It was shown recently that human glycyl-tRNA synthetase is a regulator of translational initiation of poliovirus mRNA. Details of this process and its mechanism still remain unknown. While exploring this stage of poliovirus functioning we have studied the interaction of the cytoplasmic form of human glycyl-tRNA synthetase and its domains with the fragments of the poliovirus IRES element. As a result, we have identified the minimal fragment of viral mRNA with which glycyl-tRNA synthetase fully interacts and estimated the contribution of some domains to the interaction of glycyl-tRNA synthetase with RNA.
Subject(s)
Glycine-tRNA Ligase/chemistry , RNA, Messenger/chemistry , RNA, Transfer/chemistry , Amino Acids/chemistry , Cytoplasm/chemistry , Glycine-tRNA Ligase/genetics , Humans , Poliovirus/chemistry , Poliovirus/enzymology , Protein Biosynthesis , RNA, Messenger/genetics , RNA, Transfer/geneticsABSTRACT
Bacterial Hfq proteins are structural homologs of archaeal and eukaryotic Sm/Lsm proteins, which are characterized by a 5-stranded ß-sheet and an N-terminal α-helix. Previously, it was shown that archaeal Lsm proteins (SmAP) could produce long fibrils spontaneously, in contrast to the Hfq from Escherichia coli that could form similar fibrils only after special treatment. The organization of these fibrils is significantly different, but the reason for the dissimilarity has not been found. In the present work, we studied the process of fibril formation by bacterial protein Hfq from Pseudomonas aeruginosa and archaeal protein SmAP from Methanococcus jannaschii. Both proteins have high homology with E. coli Hfq. We found that Hfq from P. aeruginosa could form fibrils after substitutions in the conserved Sm2 motif only. SmAP from M. jannaschii, like other archaeal Lsm proteins, form fibrils spontaneously. Despite differences in the fibril formation conditions, the architecture of both was similar to that described for E. coli Hfq. Therefore, universal nature of fibril architecture formed by Hfq proteins is suggested.
