title: Analysis of the secondary structure of the catalytic domain of mouse Ras exchange factor CDC25Mm.
abstract: The minimal active domain (GEF domain) of the mouse Ras exchange factor CDC25Mm was purified to homogeneity from recombinant Escherichia coli culture. The 256 amino acids polypeptide shows high activity in vitro and forms a stable complex with H-ras p21 in absence of guanine nucleotides. Circular dichroism (CD) spectra in the far UV region indicate that this domain is highly structured with a high content of alpha-helix (42%). Near UV CD spectra evidenced good signal due to phenylalanine and tyrosine while a poor contribution was elicited by the three tryptophan residues contained in this domain. The tryptophan fluorescence signal was scarcely affected by denaturation of the protein or by formation of the binary complex with H-ras p21, suggesting that the Trp residues, which are well conserved in the GEF domain of several Ras-exchange factors, were exposed to the surface of the protein and they are not most probably directly involved in the interaction with Ras proteins.
authors.affiliation: Dipartimento di Fisiologia e Biochimica Generali, Universita di Milano, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Coccetti
authors.forename: E
authors.initials: E
authors.lastname: Monzani
authors.forename: L
authors.initials: L
authors.lastname: Alberghina
authors.forename: L
authors.initials: L
authors.lastname: Casella
authors.forename: E
authors.initials: E
authors.lastname: Martegani
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002942:Circular Dichroism; D004926:Escherichia coli; D051379:Mice; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D018631:ras Proteins / Q000378:metabolism*; D020666:ras-GRF1
chemical_list: D018797:Cell Cycle Proteins; D020666:ras-GRF1; D010749:Phosphoprotein Phosphatases; D018631:ras Proteins