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Orthogonal use of a human tRNA synthetase active site to achieve multifunctionality


Protein multifunctionality is an emerging explanation for the complexity of higher organisms. In this regard, aminoacyl tRNA synthetases catalyze amino acid activation for protein synthesis, but some also act in pathways for inflammation, angiogenesis and apoptosis. It is unclear how these multiple functions evolved and how they relate to the active site. Here structural modeling analysis, mutagenesis and cell-based functional studies show that the potent angiostatic, natural fragment of human tryptophanyl-tRNA synthetase (TrpRS) associates via tryptophan side chains that protrude from its cognate cellular receptor vascular endothelial cadherin (VE-cadherin). VE-cadherin's tryptophan side chains fit into the tryptophan-specific active site of the synthetase. Thus, specific side chains of the receptor mimic amino acid substrates and expand the functionality of the active site of the synthetase. We propose that orthogonal use of the same active site may be a general way to develop multifunctionality of human tRNA synthetases and other proteins.

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Figure 1: Hypothesized mode of binding of T2-TrpRS to VE-cadherin.
Figure 2: Comparison of FL-TrpRS and T2-TrpRS for VE-cadherin−binding ability and angiostatic activity.
Figure 3: Trp-SA inhibits the T2-TrpRS−VE-cadherin interaction and the angiostatic activity of T2-TrpRS.
Figure 4: Mutagenesis studies confirming that the mechanism for T2-TrpRS's angiostatic activity involves the tryptophan and adenosine pockets of T2-TrpRS, as well as Trp2 and Trp4 of VE-cadherin.

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We thank L. Shapiro and B. Honig (Columbia University) for reviewing the manuscript and D.M. Shasby (University Iowa College of Medicine) for providing a plasmid encoding wild-type VE-cadherin-Fc. This work was supported by grants CA92577 from the US National Cancer Institute and GM 15539 and U54RR025204 from the US National Institutes of Health, and by a fellowship from the US National Foundation for Cancer Research.

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Q.Z., M.K., M.G., R.B., L.A.N., P.S. and X.-L.Y. designed the research; Q.Z., M.K., M.G., X.X., M.H., C.P., E.A., M.-H.D. and X.-L.Y. performed the research; Q.Z., M.K., M.G., R.B., W.B.K., P.S. and X.-L.Y. analyzed data; and Q.Z., M.K., M.G., P.S. and X.-L.Y. wrote the paper.

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Correspondence to Xiang-Lei Yang.

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Zhou, Q., Kapoor, M., Guo, M. et al. Orthogonal use of a human tRNA synthetase active site to achieve multifunctionality. Nat Struct Mol Biol 17, 57–61 (2010).

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