抄録
On the basis of chemical modification and X-ray
crystallography, glutamic acid at position 58
(Glu-58) of ribonuclease T1 (RNase T1) has been
identified as a catalytic residue. On the other hand,
the mutant of RNase T1 in which Glu-58 is replaced
with aspartic acid (Glu58Asp RNase T1) or alanine
(Glu58Ala RNase T1) did not lose the enzymatic
activity completely. To elucidate the mechanism of
this phenomenon as based on the three-dimensional
structure, molecular dynamics simulation and
energy minimization calculation were carried out
for the complexes of guanosine 3'-monophosphate
(3'-GMP) with Glu58Asp and Glu58Ala RNase T1.
The conformation thus obtained was compared
with that of the complex of 3'-GMP and wild-type
RNase T1. The results indicated that upon replacement
of Glu-58 with Asp or Ala, the relative position
of His-40 to 3'-GMP in the active site change in
such a way that His-40 acts as a general base
catalyst.
