2b4d: Difference between revisions

[[Image:2b4d.gif|left|200px]]<br /><applet load="2b4d" size="350" color="white" frame="true" align="right" spinBox="true"  

Spermidine/spermine N1-acetyltransferase (SSAT) is a key enzyme in the control of polyamine levels in human cells, as acetylation of spermidine and spermine triggers export or degradation. Increased intracellular polyamine levels accompany several types of cancers as well as other human diseases, and compounds that affect the expression, activity, or stability of SSAT are being explored as potential therapeutic drugs. We have expressed human SSAT from the cloned cDNA in Escherichia coli and have determined high-resolution structures of wild-type and mutant SSAT, as the free dimer and in binary and ternary complexes with CoA, acetyl-CoA (AcCoA), spermine, and the inhibitor N1,N11bis-(ethyl)-norspermine (BE-3-3-3). These structures show details of binding sites for cofactor, substrates, and inhibitor and provide a framework to understand enzymatic activity, mutations, and the action of potential drugs. Two dimer conformations were observed: a symmetric form with two open surface channels capable of binding substrate or cofactor, and an asymmetric form in which only one of the surface channels appears capable of binding and acetylating polyamines. SSAT was found to self-acetylate lysine-26 in the presence of AcCoA and absence of substrate, a reaction apparently catalzyed by AcCoA bound in the second channel of the asymmetric dimer. These unexpected and intriguing complexities seem likely to have some as yet undefined role in regulating SSAT activity or stability as a part of polyamine homeostasis. Sequence signatures group SSAT with proteins that appear to have thialysine Nepsilon-acetyltransferase activity.

Known diseases associated with this structure: Keratosis follicularis spinulosa decalvans OMIM:[[http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=313020 313020]]

2B4D is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=COA:'>COA</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Diamine_N-acetyltransferase Diamine N-acetyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.1.57 2.3.1.57] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2B4D OCA].  

[[Category: Bewley, M C.]]

[[Category: Coleman, C S.]]

[[Category: Flanagan, J M.]]

[[Category: Jiang, J S.]]

[[Category: NYSGXRC, New York Structural GenomiX Research Consortium.]]

[[Category: Pegg, A P.]]

[[Category: Studier, F W.]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:34:00 2008''