SdrX, a serine-aspartate repeat protein expressed by Staphylococcus capitis with collagen VI binding activity.

Staphylococcus capitis (S. capitis) has been implicated in a large proportion of coagulase-negative staphylococcal infections in very-low-birth-weight infants. To identify potential therapeutic targets, the S. capitis genome was probed for the presence of genes encoding microbial surface components recognizing adhesive matrix molecules (MSCRAMM). By using Southern blot analysis, an S. capitis gene, designated sdrX, that contained sequence motifs consistent with the Sdr family of MSCRAMM proteins was identified. By using monospecific antisera in Western blot and flow cytometry, SdrX was demonstrated to be expressed on the surface of S. capitis. Human collagen type VI was found to bind both the recombinant A domain of SdrX and viable S. capitis expressing SdrX. SdrX is the first collagen-binding Sdr protein described and is the first MSCRAMM protein identified in S. capitis.