JBC, Vol. 251, Issue 9, 2814-2819, May, 1976
Structural and functional interdependence of the protomers of Escherichia coli K 12 tryptophanase during binding of pyridoxal 5'-phosphate
O. Raibaud and M. E. Goldberg
It has been shown previously that the binding of pyridoxal 5'-phosphate to
Escherichia coli K 12 tryptophanase brings about an important
conformational change of the protein. The way in which this structural
change is transmitted from holoprotomers to apoprotomers is investigated
here, using hybrid molecules (between apoprotomers and irreversibly
saturated holoprotomers). It is shown that the binding of two or three
coenzyme molecules per tetramer stabilizes the whole molecule against
thermal inactivation and cold-induced dissociation. The change in
conformation induced on an apoprotomer by the proximity of three
holoprotomers is described, using three structural probes: the kinetics of
binding of the cofactor and of 5'-phosphopyridoxyl-tryptophan (an analog of
an intermediate in the catalytic reaction), and the reactivity of the
essential cysteines. The kinetic anticooperatively in the binding of
pyridoxal 5'-phosphate is confirmed, some of its parameters are determined,
and its mechanism is interpreted in relation to the coupling between the
protomers.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
