engleski

Biochemical insight into the complex of arginyl- and seryl-tRNA synthetases in methanogenic archaea

Several aminoacyl-tRNA synthetases (aaRS) are found in multi-synthetase complexes (MSC) so identification of the networks that connect possible regulatory non-synthetase proteins to synthetases or synthetases to each other and to the cellular processes they affect is a critical need. Whereas stable macromolecular assemblage have already been found in Methanothermobacter thermautotrophicus and in a variety of mammalian sources, we now attempted to delineate protein partners of seryl-tRNA synthetase (SerRS) in methanogenic archaea with yeast two-hybrid screen that facilitates construction of protein– protein linkage maps. Prey vectors were isolated and sequenced and we found that the M. thermautrophicus arginyl-tRNA synthetase (ArgRS) interacts directly with seryl-tRNA synthetase in the yeast-two hybrid assay ; native electrophoretic mobility shift assays and gel-filtration confirmed the protein association in vitro. As determined by gel-filtration, SerRS and ArgRS are present in a ~180-kilodalton complex with probable stoichiometry of one dimeric SerRS per ArgRS monomer. Further, we characterized the binding affinity of SerRS to ArgRS by surface plasmon resonance using BIAcore and a dissociation equilibrium constant of 300 nM was defined. Moreover, interaction of SerRS with ArgRS improves the activity of SerRS two-fold while the presence of SerRS did not lead to significant enhancement of ArgRS activity. Interestingly, SerRS has never been found associated to another synthetase or within the MSC. This type of structural organization was though to be restricted to eukaryotic species but archaeal requirements for aaRS associations are becoming more evident, as these proteins can function together in many important biological contexts such as translation and substrate channeling.

seryl-tRNA synthetase; multi-synthetase complexes; protein-protein interaction

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