A gene encoding leghaemoglobin a from soybean has been constructed and
the soluble recombinant protein expressed in E. coli. The integrity o
f the recombinant protein has been assessed by a range of spectroscopi
c techniques. Electrospray mass spectrometry of the protein indicates
that the molecular mass of the protein corresponds to the predicted am
ino acid sequence. Circular dichroism spectra of the ferric derivative
and UV-visible spectra of various ferric and ferrous derivatives (pH
6.99, mu = 0.10 M, 25.0 degrees C) are consistent with published data
for the wild-type protein. For the ferric derivative, UV-visible (298
and 77 K) and EPR (10 K) spectra indicate the existence of a thermal e
quilibrium between high-and low-spin forms. Titration of the protein (
0.10 M NaCl, mu = 0.10 M, 25.0 degrees C) between pHs 6.68 and 10.35 i
ndicate formation (pK(a) = 8.3 +/- 0.03) of a 6-coordinate, hydroxide-
bound form of the protein at high pH. All of the above data are consis
tent with the behaviour of the wild-type protein.