Conformational structure and binding mode of glyceraldehyde-3-phosphate dehydrogenase to tRNA studied by Raman and CD spectroscopy

Recently it has been suggested that glyceraldehyde-3-phosphate dehydrogenas e (GAPDH) plays a role in nuclear tRNA export. As the structural basis of b inding of GAPDH to tRNA is as yet unknown, we have employed Raman and CD sp ectroscopy as probes of the solution structures of GAPDH from rabbit and tR NA(Phe) from brewers yeast. Additionally, we have obtained the Raman and CD spectra of GAPDH when bound to tRNAPhe. In the complex we find the followi ng results: (a) The most part of the tRNA(Phe) structure is conserved, but with a slight perturbation toward a B-like form. (b) No significant changes in the secondary structure of the protein, upon binding are observed. (c) The surface enhanced Raman spectra are consistent with a GAPDH-tRNA(Phe) co mplex molecular model that involves the insertion of tRNA(Phe) into the GAP DH tetramer groove containing the R and P axes. (d) The specific interactio ns that occur between GAPDH and the tRNA(Phe) involve, mainly, stacking bet ween nucleobases and aromatic amino-acid residues, and ionic interactions o f basic amino-acid residues with phosphate groups of the ribose-phosphate b ackbone. The above stacking interactions are also supported by the signific ant relatedness that we have found between an amino-acid sequence (residues 303-308) of GAPDH and RNP2 binding motifs of some RNA binding proteins. (C ) 1999 Elsevier Science B.V. All rights reserved.