title: Affinity labeling of ras oncogene product p21 with guanosine diphospho- and triphosphopyridoxals.
abstract: Purified v-rasH p21 overproduced in Escherichia coli was treated with guanosine diphospho- and triphosphopyridoxals (GP2- and GP3-PL), affinity labeling reagents specific to a lysyl residue located in the guanine nucleotide binding site. GP2-PL and GP3-PL inhibited [3H]GDP binding to p21 competitively. Incubation of p21 with GP2-PL and GP3-PL followed by reduction with NaBH4 resulted in 40 and 50% loss of [3H]GDP binding activity, respectively, whereas the addition of excess GDP completely protected p21 from the inactivation. The tryptic digest of p21 which was modified with GP2-PL or GP3-PL in the presence or absence of protective GDP and subsequently reduced by NaBH4 was analyzed by reverse phase high performance liquid chromatography. The profile of the effluent monitored by the fluorescence from the pyridoxyl moiety showed the existence of peptides which were specifically labeled only in the absence of GDP. Structural analyses of these peptides allowed us to identify the labeled residue as Lys-16. These results suggest that Lys-16 is located in the guanine nucleotide binding site, close to the beta- or gamma-phosphate group of the nucleotide.
mesh_terms: D000345:Affinity Labels / Q000378:metabolism*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001667:Binding, Competitive; D004926:Escherichia coli / Q000235:genetics; D011905:Genes, ras; D006150:Guanine Nucleotides; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D008239:Lysine; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D014357:Trypsin
chemical_list: D000345:Affinity Labels; D000596:Amino Acids; D006150:Guanine Nucleotides; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; C057277:guanosine diphosphopyridoxal; C057278:guanosine triphosphopyridoxal; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D014357:Trypsin; D016283:Proto-Oncogene Proteins p21(ras); D008239:Lysine