A new domain family in the superfamily of alkaline phosphatases.

During the course of our large-scale genome analysis a conserved domain, currently detectable only in the genomes of Drosophila melanogaster, Caenorhabditis elegans and Anopheles gambiae, has been identified. The function of this domain is currently unknown and no function annotation is provided for this domain in the publicly available genomic, protein family and sequence databases. The search for the homologues of this domain in the non-redundant sequence database using PSI-BLAST, resulted in identification of distant relationship between this family and the alkaline phosphatase-like superfamily, which includes families of aryl sulfatase, N-acetylgalactosomine-4-sulfatase, alkaline phosphatase and 2,3-bisphosphoglycerate-independent phosphoglycerate mutase (iPGM). The fold recognition procedures showed that this new domain could adopt a similar 3-D fold as for this superfamily. Most of the phosphatases and sulfatases of this superfamily are characterized by functional residues Ser and Cys respectively in the topologically equivalent positions. This functionally important site aligns with Ser/Thr in the members of the new family. Additionally, set of residues responsible for a metal binding site in phosphatases and sulphtases are conserved in the new family. The in-depth analysis suggests that the new family could possess phosphatase activity.

SUPFAM: a database of sequence superfamilies of protein domains.

BACKGROUND: SUPFAM database is a compilation of superfamily relationships between protein domain families of either known or unknown 3-D structure. In SUPFAM, sequence families from Pfam and structural families from SCOP are associated, using profile matching, to result in sequence superfamilies of known structure. Subsequently all-against-all family profile matches are made to deduce a list of new potential superfamilies of yet unknown structure. DESCRIPTION: The current version of SUPFAM (release 1.4) corresponds to significant enhancements and major developments compared to the earlier and basic version. In the present version we have used RPS-BLAST, which is robust and sensitive, for profile matching. The reliability of connections between protein families is ensured better than before by use of benchmarked criteria involving strict e-value cut-off and a minimal alignment length condition. An e-value based indication of reliability of connections is now presented in the database. Web access to a RPS-BLAST-based tool to associate a query sequence to one of the family profiles in SUPFAM is available with the current release. In terms of the scientific content the present release of SUPFAM is entirely reorganized with the use of 6190 Pfam families and 2317 structural families derived from SCOP. Due to a steep increase in the number of sequence and structural families used in SUPFAM the details of scientific content in the present release are almost entirely complementary to previous basic version. Of the 2286 families, we could relate 245 Pfam families with apparently no structural information to families of known 3-D structures, thus resulting in the identification of new families in the existing superfamilies. Using the profiles of 3904 Pfam families of yet unknown structure, an all-against-all comparison involving sequence-profile match resulted in clustering of 96 Pfam families into 39 new potential superfamilies. CONCLUSION: SUPFAM presents many non-trivial superfamily relationships of sequence families involved in a variety of functions and hence the information content is of interest to a wide scientific community. The grouping of related proteins without a known structure in SUPFAM is useful in identifying priority targets for structural genomics initiatives and in the assignment of putative functions. Database URL: http://pauling.mbu.iisc.ernet.in/~supfam.