Biochemical and genetic analysis of Streptococcus mutans alpha-galactosidase.
The aga gene coding for alpha-galactosidase in Streptococcus mutans was detected in a recombinant gene library constructed in phage lambda. The gene was subcloned into plasmid vectors and shown to specify a novel protein of Mr 80,000. Characterization of alpha-galactosidase from S. mutans and from recombinant Escherichia coli expressing aga indicated that the enzyme functions as a tetramer. The amino acid composition of the alpha-galactosidase, deduced from nucleotide sequencing of aga, gave a predicted Mr of 82,022 and revealed regions of homology to alpha-galactosidases encoded by the E. coli Raf plasmids and by Bacillus stearothermophilus. Inactivation of the aga gene in S. mutans resulted in loss of all alpha-galactosidase activity and abolished the ability to ferment melibiose; alpha-glucosidase activity was also lost, due to an indirect effect on the dexB gene.
Aduse-Opoku
J
J
Hunterian Dental Research Unit, London Hospital Medical College, UK.
Tao
L
L
Ferretti
J J
JJ
Russell
R R
RR
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial; D004591:Electrophoresis, Polyacrylamide Gel; D004790:Enzyme Induction; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D013295:Streptococcus mutans / Q000201:enzymology / Q000235:genetics*; D000519:alpha-Galactosidase / Q000235:genetics* / Q000378:metabolism
D004269:DNA, Bacterial; D000519:alpha-Galactosidase