137. Abstract
Photoaffinity labeling of purified cellulose
synthase with [-32P]5-azidouridine 5'-diphosphoglucose
(UDP-Glc) has been used to identify the UDP-Glc binding subunit
of the cellulose synthase from Acetobacter xylinum strain
ATCC 53582. The results showed exclusive labeling of an 83-kDa
polypeptide. Photoinsertion of [-32P]5-azido-UDP-GIc
is stimulated by the cellulose synthase activator, bis-(3'5')
cyclic diguanylic acid. Addition of increasing amounts of UDP-Glc
pre-vents photolabeling of the 83-kDa polypeptide. The reversible
and photocatalyzed binding of this photoprobe also showed saturation
kinetics. These studies demonstrate that the 83-kDa polypeptide
is the catalytic subunit of the cellulose synthase in A. xylinum
strain ATCC 53582.