Abstract
RNase T1 has two isozymes, Gln25- and Lys25-isoforms. The latter is relatively more stable than
the former, although enzymatic activities are the
same in both isozymes. Conformations of the two
isoforms are not distinguished from each other
crystallographically. To elucidate the mechanism of
this phenomenon as based on the three-dimensional
structure, energy minimization calculations with
and without restraints were carried out for the
complexes of guanosine 3'-monophosphate (3'-GMP)
with Lys25-RNase T1. The results indicated
that the stability is mainly due to the electrostatic
interaction of Lys25 with Asp29 and/or Glu31, not
with Glu28 as reported previously.
