Conformational effects of nucleotide exchange in ras p21 proteins as studied by fluorescence spectroscopy.
The intrinsic fluorescence properties of the oncogene protein p21N-ras,p21H-ras and one of its transforming mutants, p21N-ras (Val12), have been investigated. A mutant containing a single tryptophan at position 28 in p21H-ras (Trp28) has been specifically engineered to provide a probe of protein conformation on nucleotide binding. The proteins produced essentially similar circular dichroism spectra typical of alpha/beta proteins. A decrease in the intensity of the fluorescence emission spectrum due to tyrosine occurred on GDP/GTP nucleotide exchange in the native and mutant proteins. Selective excitation of the single tryptophan in p21 produced a decrease in fluorescence intensity which was accompanied by a blue shift in the wavelength of maximum emission on nucleotide exchange. A reduction in the residual Mg2+ ion concentration enhanced this effect.
Skelly
J V
JV
CRC Biomolecular Structure Unit, Institute of Cancer Research, Sutton, Surrey, England.
Suter
D A
DA
Kuroda
R
R
Neidle
S
S
Hancock
J F
JF
Drake
A
A
D002942:Circular Dichroism; D004492:Edetic Acid / Q000494:pharmacology; D005453:Fluorescence; D006150:Guanine Nucleotides / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D015689:Oncogene Protein p21(ras); D011487:Protein Conformation
D006150:Guanine Nucleotides; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D004492:Edetic Acid; D015689:Oncogene Protein p21(ras); D008274:Magnesium