PURIFICATION OF THE MUTX PROTEIN OF STREPTOCOCCUS-PNEUMONIAE, A HOMOLOG OF ESCHERICHIA-COLI MUTT - IDENTIFICATION OF A NOVEL CATALYTIC DOMAIN FOR NUCLEOSIDE TRIPHOSPHATE PYROPHOSPHOHYDROLASE ACTIVITY
Lc. Bullions et al., PURIFICATION OF THE MUTX PROTEIN OF STREPTOCOCCUS-PNEUMONIAE, A HOMOLOG OF ESCHERICHIA-COLI MUTT - IDENTIFICATION OF A NOVEL CATALYTIC DOMAIN FOR NUCLEOSIDE TRIPHOSPHATE PYROPHOSPHOHYDROLASE ACTIVITY, The Journal of biological chemistry, 269(16), 1994, pp. 12339-12344
The mutX gene of Streptococcus pneumoniae, a homologue of the Escheric
hia coli mutT mutator gene (Mejean, V., Salles, C., Bullions, L. C., B
essman, M. J., and Claverys, J.-P. (1993) Mol. Microbiol. 11, 323-330)
has been cloned into an expression vector, and its gene product, the
MutX protein, has been purified to apparent homogeneity. Like MutT, th
e pure MutX protein hydrolyzes all of the canonical nucleoside triphos
phates at different rates with a preference for dGTP, yielding nucleos
ide monophosphates and inorganic pyrophosphate. Despite this similarit
y in enzymatic activity, the two proteins have notably dissimilar prim
ary and quaternary structures, They share only a small region of amino
acid homology, and under the same conditions in which MutT exists as
a monomer in solution, MutX behaves as a trimer. The small region of c
onserved amino acid sequence most likely identifies a protein domain r
esponsible for the novel nucleoside triphosphate pyrophosphohydrolase
activity shared by the two enzymes, and by another protein of unknown
function, the product of the E. coli orf17 gene (Takahagi, M., Iwasaki
, H., Nakata, A., and Shinegawa, H. (1991) J. Bacteriol. 173, 5747-575
3).