F. Sica et al., Crystallization of multiple forms of bovine seminal ribonuclease in the liganded and unliganded state, J CRYST GR, 196(2-4), 1999, pp. 305-312
Bovine seminal ribonuclease (BS-RNase) is an intriguing homodimeric enzyme
which exists as two conformational isomers, characterized by distinct catal
ytic and biological properties, referred to as M x M and M = M. Reduction o
f inter-chain disulfide bridges produces a stable monomeric derivative (M)
which is still active. This paper reports the screening and optimization of
crystallization conditions for growing single diffraction-quality crystals
for the various BS-RNase forms. The crystallization trials were performed
using both the vapor diffusion and microbatch methods. The M x M dimer was
crystallized in the free form from polyethylene glycol (PEG) 4000 at pH 8.5
and as a complex with the substrate analog uridylyl(2'-5')guanosine (UpG)
from an unbuffered ammonium sulfate (AS) solution. These two crystal types
diffract X-rays to 2.5 and 1.9 Angstrom resolution, respectively. Two diffe
rent crystal types were obtained both for the M = M dimer and for the monom
eric derivative. (M = M)a crystals, grown from PEG 4000 (8% w/v) at pH 5.6,
diffract X-rays to 4.0 Angstrom. At higher PEG concentration (15% w/v) a d
ifferent crystal type was obtained, (M = M)b, which showed a better diffrac
tion limit (2.5 Angstrom). For the monomer, type (M)a and (M)b crystals, di
ffracting X-rays to 2.5 a resolution, were obtained from AS at pH 6.5 and f
rom PEG 4000 at pH 8.5, respectively. A comparison with previously crystall
ized forms of the dimer M x M and its complexes with uridylyl(2'-5')adenosi
ne and 2'-deoxycytidylyl(3'-5')-2'-deoxyadenosine is also presented. The th
ree-dimensional structure analysis of (M x M)UpG and (M = M)b is in progres
s. (C) 1999 Elsevier Science B.V. All rights reserved.