Role of forefinger and thumb loops in production of ?54 and ?55 in tRNAs by archaeal Pus10.

ABSTRACT: Pseudouridines (?) are found in structurally and functionally important regions of RNAs. Six families of ? synthases, TruA, TruB, TruD, RsuA, RluA, and Pus10 have been identified. Pus10 is present in Archaea and Eukarya. While most archaeal Pus10 produce both tRNA ?54 and ?55, some produce only ?55. Interestingly, human PUS10 has been implicated in apoptosis and Crohn's and Celiac diseases. Homology models of archaeal Pus10 proteins based on the crystal structure of human PUS10 reveal that there are subtle structural differences in all of these Pus10 proteins. These observations suggest that structural changes in homologous proteins may lead to loss, gain, or change of their functions, warranting the need to study the structure-function relationship of these proteins. Using comparison of structural models and a series of mutations, we identified forefinger loop (reminiscent of that of RluA) and an Arg and a Tyr residue of archaeal Pus10 as critical determinants for its ?54, but not for its ?55 activity. We also found that a Leu residue, in addition to the catalytic Asp, is essential for both activities. Since forefinger loop is needed for both rRNA and tRNA ? synthase activities of RluA, but only for tRNA ?54 activity of Pus10, archaeal Pus10 proteins must use a different mechanism of recognition for ?55 activity. We propose that archaeal Pus10 uses two distinct mechanisms for substrate uridine recognition and binding. However, since we did not observe any mutation that affected only ?55 activity, both mechanisms for archaeal Pus10 activities must share some common features.

SUBMITTER: Joardar A 

PROVIDER: S-EPMC3753934 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature