This web page was produced as an assignment for Gen677 at UW-Madison Spring 2009
Profile Structure Homology Phylogeny
Domains, structure, and Family
I chose to use PFAM as a source of protein information on this gene. I found the SMART database to be less useful because my gene only had PFAM domains and the SMART database simply linked me to those.
SRD5A2 belongs to the Steroid-dh family, which is also part of a clan that contains a series of carboxy methyltransferases.
Each of the homologous sequences, including Arabidopsis, contain the C-terminal steroid_dh domain. The sequence lacks any N- or O-linked glycosylation sequences. The amino acid sequences is also scattered with 37% hydrophobic residues(3). This is in agreement with the PFAM prediction of several tansmembrane sequences. Also, a TMHMM query showed multiple areas likely to be transmembrane structures (see left)
Post Translational Modification Domains
A MOTIF Scan uncovered a few post translational modification sites. There were 4 N-myristoylation sites, 3 protein kinase C phosphorylation sites, and a single tyrosine kinase phosphorylation sites. See image for a respective example site of each type of modification.
Above is the ProSite sequence logo for the C-Terminal steroid_dh across multiple organisms. There are a variety of residues that are constant and some that are variable. However, in all cases the enzyme functions as a steroid reductase. Again its worth noting that the center of the sequence seems to be slightly more conserved, indicative of the enzyme's active site.
Cleavage of SRD5A2
According to PeptideCutter, Trypsin will cleave this protein in 17 spots(see example below). This occurs preferentially after arginine and lysine residues (4), which are fairly common in this sequence. Interestingly though, most members of the caspase family do not affect this structure.
References
1. The Pfam protein families database: R.D. Finn, J. Tate, J. Mistry, P.C. Coggill, J.S. Sammut, H.R. Hotz, G. Ceric, K. Forslund, S.R. Eddy, E.L. Sonnhammer and A. Bateman Nucleic Acids Research (2008) Database Issue 36:D281-D288
2. PROSITE
3. Russell, D. W., and Wilson, J.D. 1994. Steroid 5alpha-Reductase:Two genes/Two Enzymes. Annu. Rev. Biochem. 63:25-61, doi:10.1146/annurev.bi.63.070194.000325
4. Keil, B. Specificity of Proteolysis. Springer-Verlag Berlin-Heidelberg-NewYork, pp.335. (1992)
5. Transmembrane helice prediction:TMHMM
