Regulation of Streptococcus gordonii sspB by the sspA gene product - PubMed (original) (raw)

Regulation of Streptococcus gordonii sspB by the sspA gene product

A El-Sabaeny et al. Infect Immun. 2001 Oct.

Abstract

Streptococcus gordonii expresses two related adhesins, SspA and SspB, the genes for which are adjacent on the chromosome and are regulated independently. Although the adhesins are functionally similar, the sspA promoter is more active than that of sspB. In this study we show an additional role for SspA in the control of sspB activity. Gel shift and DNA footprinting assays demonstrate that the SspA protein binds to the sspB promoter and protects a region 233 to 264 bp upstream of the predicted -35 promoter element. The responsiveness of the sspB promoter to SspA was investigated with a promoter-cat reporter. Expression of the sspB promoter was reduced by over 60% in an SspA-deficient mutant of S. gordonii. These results indicate that expression of S. gordonii sspB is positively regulated by the sspA gene product.

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Figures

FIG. 1

FIG. 1

Electrophoretic mobility shift analysis of binding of SspA to the sspB upstream promoter-containing region. A 364-bp 32P-labeled sspB upstream fragment was used as the probe. Reaction mixtures contained probe alone (lane 1), probe with SspA protein (lane 2), probe with SspA and excess unlabeled probe (lane 3), probe with SspA protein and excess E. coli DNA (lane 4), or probe with sonicated E. coli extract containing cloned DNA binding domain from EBNA-1 (lane 5).

FIG. 2

FIG. 2

(A) DNase I footprint of protection by SspA of a 279-bp sspB upstream region. Lane 1, Maxam and Gilbert A+G ladder; lanes 2 to 5, DNase I treatment in the presence of 0, 1, 2, and 4 μg of SspA, respectively. The 32-bp protected sequence is indicated by a bracket. (B) DNA sequence upstream of sspB. The 32-bp region protected from DNase I digestion is underlined.

FIG. 3

FIG. 3

Growth phase and expression of sspB in an SspA+ (strain HA00) or SspA− (strain HA02) background. Optical densities (O.D.) and CAT activities were measured at different incubation times. The data are from a representative of three experiments.

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