Human Spermine spermidine acetyltransferase K26R mutant

Experimental Data Snapshot

  • Resolution: 1.85 Å
  • R-Value Free: 0.240 
  • R-Value Work: 0.210 
  • R-Value Observed: 0.210 

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Structures of wild-type and mutant human spermidine/spermine N1-acetyltransferase, a potential therapeutic drug target.

Bewley, M.C.Graziano, V.Jiang, J.Matz, E.Studier, F.W.Pegg, A.E.Coleman, C.S.Flanagan, J.M.

(2006) Proc Natl Acad Sci U S A 103: 2063-2068

  • DOI: https://doi.org/10.1073/pnas.0511008103
  • Primary Citation of Related Structures:  
    2B3U, 2B3V, 2B4B, 2B4D, 2B58, 2B5G

  • 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.

  • Organizational Affiliation

    Biology Department, Brookhaven National Laboratory, Upton, NY 11973, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Diamine acetyltransferase 1
A, B
171Homo sapiensMutation(s): 1 
Gene Names: SAT
UniProt & NIH Common Fund Data Resources
Find proteins for P21673 (Homo sapiens)
Explore P21673 
Go to UniProtKB:  P21673
GTEx:  ENSG00000130066 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP21673
Sequence Annotations
  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on MSE
A, B
Experimental Data & Validation

Experimental Data

  • Resolution: 1.85 Å
  • R-Value Free: 0.240 
  • R-Value Work: 0.210 
  • R-Value Observed: 0.210 
  • Space Group: P 43
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 74.3α = 90
b = 74.3β = 90
c = 63.3γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
SCALEPACKdata scaling
HKL-2000data reduction

Structure Validation

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Entry History 

Revision History  (Full details and data files)

  • Version 1.0: 2006-01-17
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2015-06-24
    Changes: Data collection, Database references
  • Version 1.4: 2021-02-03
    Changes: Database references, Derived calculations, Structure summary