Involved in the biosynthesis of 6-O-methylglucose lipopolysaccarides (MGLPs). Catalyzes the transfer of a glucose (Glc) moiety from uridine diphosphate (UDP-Glc) to the position 2 of 3-phospho-D-glycerate (3-PGA) to form glucosyl-3-phosphoglycerate (GPG). (2R)-3-phosphoglycerate + an NDP-alpha-D-glucose = (2R)-2-O-(alpha-D-glucopyranosyl)-3-phospho-glycerate + a ribonucleoside 5'-diphosphate + H(+) Requires divalent cations for activity in the following order of efficiency: Mn(2+), Co(2+) and Mg(2+) ions. Optimum pH is 7.5-8.5. Optimum temperature is 50 degrees Celsius. Belongs to the glycosyltransferase 2 family.