Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.3 (RNase T1)
 1,228 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The binding of ribonuclease T1 with guanosine (Guo) and deoxyguanosine (dGuo) was studied in experiments employing ultraviolet difference spectroscopy in the pH range 3-9 at 0.2 M ionic strength and 25 degrees C. Similar experiments were also conducted with psi-carboxymethyl-glutamate-58 ribonuclease T1 at pH 5.0. At most pH values the characteristic difference spectrum and association constant were obtained. The binding constant for dGuo was approximately 550 M-1 and did not significantly vary in the pH range 3.5-9.0. The binding constant for Guo increased from pH 3.5 to 5.0, was constant between pH 5.0 and 7.0 (approximately 3200 M-1), and decreased at higher pH values. The binding of Guo and dGuo with ribonuclease T1 could also be distinguished in terms of the wavelength for maximal difference absorbance, lambdamax, between pH 5.0 and 7.0. At higher and lower pH values, lambdamax for Guo approached that found fr dGuo. On the other hand, the value of the binding constant (approximately6500 M-1) and the nature of the difference spectra for Guo and dGuo binding with lambdamax-carboxymethyl-glutamate-58-ribonuclease T1 at pH 5.0 were identical. These results suggest that the discrete interaction of the Guo 2'-hydroxyl group with ribonuclease T1 involves the lambda-carboxylate of glutamate-58 and an imidazolium group at the active site.
 ...
PMID:Ribose recognition by ribonuclease T1: difference spectral binding studies with guanosine and deoxyguanosine. 0 71

The enzymatic activity of many ribonucleases (RNases) depends on two histidines, as in RNase A, or one histidine and/or glutamate, as in microbial RNases belonging to the T1 family. In RNase T1, substitution of either one or both of the two histidines at positions 40 and 92 by a variety of other amino acids reduces the activity more than 100-fold. However, the double variant His40-->Asp/His92-->Asp retains a significant residual enzymatic activity towards RNA and guanylyl-3',5'-cytidine, indicating that a pair of substituted side chains in these positions, both with acid functionality, can confer enzymatic activity. It was shown that the substitution of histidine with glutamate in the variant His40-->Glu yields an enzyme with drastically reduced activity and leads to inactivation in the His92-->Glu, His40-->Glu/His92-->Glu variants. For the variants where histidine is substituted with aspartate we found measurable activity from 1% (His40-->Asp) to 6% (His40-->Glu/His92-->Asp) towards RNA.
 ...
PMID:Ribonuclease T1 is active when both catalytic histidines are replaced by aspartate. 922 37