GalR Acts as a Transcriptional Activator of galKT in the Presence of Galactose in Streptococcus pneumoniae

Abstract

We explored the regulatory mechanism of Leloir pathway genes in <i>Streptococcus pneumoniae</i> D39. Here, we demonstrate that the expression of <i>galKT</i> is galactose dependent. By microarray analysis and quantitative RT-PCR, we further show the role of the transcriptional regulator GalR, present upstream of <i>galKT</i>, as a transcriptional activator of <i>galKT</i> in the presence of galactose. Moreover, we predict a 19-bp regulatory site (5′-GATAGTTTAGTAAAATTTT-3′) for the transcriptional regulator GalR in the promoter region of <i>galK</i>, which is also highly conserved in other streptococci. Growth comparison of D39 &#x0394;<i>galK</i> with the D39 wild type grown in the presence of galactose shows that <i>galK</i> is required for the proper growth of <i>S. pneumoniae</i> on galactose.