Involved in the biosynthesis of 6-O-methylglucose lipopolysaccarides (MGLPs) (PubMed:18221489, PubMed:19421329). Catalyzes the transfer of the glucose moiety from a nuleotide sugar such as UDP-alpha-D-glucose to the position 2 of 3-phospho-D-glycerate (3-PGA) to form glucosyl-3-phosphoglycerate (GPG). It can use UDP-glucose, ADP-glucose and GDP-glucose as sugar donor substrates with decreasing affinity and with 3-PGA as an acceptor. D-glycerate can only be an acceptor with ADP-glucose and at a very low rate (PubMed:18221489). (2R)-3-phosphoglycerate + an NDP-alpha-D-glucose = (2R)-2-O-(alpha-D-glucopyranosyl)-3-phospho-glycerate + a ribonucleoside 5'-diphosphate + H(+) (2R)-3-phosphoglycerate + UDP-alpha-D-glucose = (2R)-2-O-(alpha-D-glucopyranosyl)-3-phospho-glycerate + H(+) + UDP (2R)-3-phosphoglycerate + ADP-alpha-D-glucose = (2R)-2-O-(alpha-D-glucopyranosyl)-3-phospho-glycerate + ADP + H(+) (2R)-3-phosphoglycerate + GDP-D-glucose = (2R)-2-O-(alpha-D-glucopyranosyl)-3-phospho-glycerate + GDP + H(+) Requires divalent cations for activity. The maximum activity is observed at 20 mM of MgCl(2). Optimum pH is 8. Optimum temperature is 45 degrees Celsius. The activity is undetectable below 20 and above 55 degrees Celsius. Homotrimer. Disruption reduces growth rate and results in an 80% decrease in the production of methylglucose lipopolysaccharides (MGLPs) directly attributable to a drastic if not complete loss of GPG synthesis. Belongs to the glycosyltransferase 2 family. Extended N-terminus.