2B3U

Human Spermine spermidine acetyltransferase K26R mutant

Summary for 2B3U

• Entry DOI: 10.2210/pdb2b3u/pdb
• Related: 2B3V 2B47 2B4B 2B4D 2B5G
• Descriptor: Diamine acetyltransferase 1, SULFATE ION (3 entities in total)
• Functional Keywords: acyltransferase, structural genomics, psi, protein structure initiative, new york sgx research center for structural genomics, nysgxrc, transferase
• Biological source: Homo sapiens (human)
• Total number of polymer chains: 2
• Total formula weight: 41000.66

Authors

Bewley, M.C.,Graziano, V.,Jiang, J.S.,Matz, E.,Studier, F.W.,Pegg, A.P.,Coleman, C.S.,Flanagan, J.M.,Burley, S.K.,New York SGX Research Center for Structural Genomics (NYSGXRC) (deposition date: 2005-09-21, release date: 2006-01-17, Last modification date: 2024-11-06)

Primary citation

Bewley, M.C.,Graziano, V.,Jiang, J.,Matz, E.,Studier, F.W.,Pegg, A.E.,Coleman, C.S.,Flanagan, J.M.
Structures of wild-type and mutant human spermidine/spermine N1-acetyltransferase, a potential therapeutic drug target.
Proc.Natl.Acad.Sci.USA, 103:2063-2068, 2006

PubMed Abstract: 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.

PubMed: 16455797
DOI: 10.1073/pnas.0511008103

Experimental method

X-RAY DIFFRACTION (1.85 Å)