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Average AF2095 (GR4) structure
Journal of Biomolecular NMR (2004), 30, 107-108. |
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The thermophilic archaea Archaeglobus fulgidis AF2095 protein is an example of a protein of unknown biological function targeted for structural analysis by the Northeast Structural Genomics Consortium (NESG), which also belongs to the previously unannotated Pfam family UPF0099. Comparison of the 3D NMR structure of A. fulgidis AF2095 and the 1.95-Å X-ray crystal structure of the functionally-unannotated thermophilic archaea T. acidophilum protein TA0108 that has recently been deposited in the Protein Database (PDB ID: 1RLK) with the human Pth2 X-ray structure suggest that these proteins are also Pth2 enzymes.
Peptidyl-tRNA hydrolase (Pth) is a crucial bacterial enzyme. Peptidyl-tRNA hydrolase cleaves the peptide from peptidyl-tRNA molecules that have prematurely dissociated from the ribosome during protein translation. The freed tRNA can then be recycled back into the protein synthesis process. Aminoacyl tRNAfMet, the initiator of the translation process, is a relatively poor substrate for E. coli Pth and is correspondingly protected from hydrolysis. This permits free aminoacyl tRNAfMet to readily participate in the formation of the relatively slow ribosomal initiation complex without being prematurely hydrolyzed.
Although it had been proposed that the Pth2 family has no bacterial members, assessments of homology models based on the 3D structure of AF2095 reported here demonstrates a wide phylogenetic distribution of the Pth2 enzyme class, including many bacterial proteins, consistent with the recent inclusion of bacterial members in Pfam family UPF0099. Phylogenic analysis of the Pth2 enzymes homologous to AF2095 supports convergent evolution of the Pth and Pth2 enzymes suggesting that eukaryotes inherited Pth2 as part of the mitochondria organelle.