TRANSPORT OF SUGARS, INCLUDING SUCROSE, BY THE MSM TRANSPORT-SYSTEM OF STREPTOCOCCUS-MUTANS

The range of substrates transported by the sugar-binding protein-depen dent msm (multiple sugar metabolism) system of S. mutans was investiga ted. By determining the ability of unlabeled sugar to compete with rad iolabeled melibiose transport, we have demonstrated that the transport ed sugars included a number of carbohydrates structurally related to r affinose. A model accommodating these results has been devised which a ccounts for the sugars transported by the msm transport system. Compet ition with radiolabeled melibiose transport indicated sucrose to be an msm substrate. This was confirmed by examination of uptake of radiola beled sucrose in scrAB mutants lacking the sucrose-specific phosphotra nsferase system.