933 Structural Analysis of a Streptococcal Domain of Unknown Function(DUF1792)

Friday, March 23, 2012: 2 p.m. - 3:15 p.m.
Presentation Type: Poster Session
H. ZHANG1, F. ZHU1, M. ZHOU1, L. DING2, and H. WU1, 1School of Dentistry, University of Alabama at Birmingham, Birmingham, AL, 2University of Alabama at Birmingham, Birmingham, AL
        Serine-rich repeat proteins (SRRPs) belong to a growing family of bacterial adhesins required for biofilm formation and pathogenesis. Fap1 from Streptococcus parasanguinis is the first SRRP identified. A number of genes involved in Fap1 glycosylation have been characterized. Glycosyltransferases Gtf1, Gtf2 and Gtf3 catalyze the first and second steps of Fap1 glycosylation. A glycosyltransferase, GalT1, catalyzes the third step of Fap1 glycosylation.  At the N-terminus of GalT1, there is a domain of unknown function 1792 (DUF1792) that is highly conserved in bacteria and may constitute a broad protein superfamily, however its function is unknown.

Objective: Solve 3-D structure of DUF1792 to determine the function of the domain

Method:   The recombinant DUF1792 protein was purified via Ni2+ affinity chromatography and gel filtration. The hanging-drop vapor-diffusion method was used for the crystallization trials. The structure was determined by multiwavelength anomalous diffraction (MAD) utilizing Se atoms as the anomalous scatterers. The Gtf1-2-3 modified Fap1 was purified and used as a substrate to determine in vitro glycosyltransferase activity of DUF1792. An E. coli glycosylation system consisting of Fap1 substrate and respective glycosyltransferases was established to determine in vivo glycosylation activity.

Result:  A 3-D X-ray crystallographic structure of DUF1792 was determined at the resolution of 1.5 Å. The structure is composed of two N-terminal α/β/α sandwich domains, a C-terminal β/α/β Rossmann domain and a long-loop. In vitro and in vivo glycosyltransferase assays revealed that DUF1792 possesses glycosyltransferase activity, and the activity is conserved in other streptococci. A new metal binding motif required for glycosyltransferase activity was identified.

Conclusion: Since no sequence and structure homology analysis indicated DUF1792 as a glycosyltransferase, we concluded that DUF1792 represents a new family of glycosyltransferases.

This abstract is based on research that was funded entirely or partially by an outside source: NIH/NIDCR R01 DE017954

Keywords: Adhesion, Microbiology and Structure