Transport of Lysine and Hydroxylysine in Streptococcus faecalis

Abstract

Data are presented which support the view that l -lysine is transported by two systems in Streptococcus faecalis . The system with the higher affinity for l -lysine appears to be specific for l -lysine among the common amino acids and to require an energy source. The second system transports both l -lysine and l -arginine and does not appear to require an energy source. Both of these systems will accept hydroxy- l -lysine as a substrate as shown by the energy requirement for hydroxy- l -lysine transport and by the inhibition of uptake by l -arginine as well as by l -lysine. The affinity of both systems appears to be considerably lower for hydroxy- l -lysine than for l -lysine. A mutant of S. faecalis which is resistant to the growth inhibitory action of hydroxy- l -lysine appears to differ from the parent strain by having a defective l -lysine-specific transport system. In this mutant, hydroxy- l -lysine is not readily transported via the l -lysine-specific system because of the mutation or via the second system because of the high concentration of l -arginine present in the growth medium. This overall lack of transport prevents hydroxy- l -lysine from reaching inhibitory levels within the cell.