PDBsum entry 2b5g

Transferase

PDB id: 2b5g

Contents

Protein chains

164 a.a. *

160 a.a. *

Ligands

SO4 ×7

Waters ×323

* Residue conservation analysis

PDB id:

2b5g

Name:

Transferase

Title:

Wild type ssat- 1.7a structure

Structure:

Diamine acetyltransferase 1. Chain: a. Synonym: spermidine/spermine n1, - acetyltransferase 1, ssat, ssat-1, putrescine acetyltransferase, polyamine n-acetyltransferase 1. Engineered: yes. Diamine acetyltransferase 1. Chain: b. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: sat. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.70Å R-factor: 0.211 R-free: 0.241

Authors:

M.C.Bewley,V.Graziano,J.S.Jiang,E.Matz,F.W.Studier,A.P.Pegg, C.S.Coleman,J.M.Flanagan,S.K.Burley,New York Sgx Research Center For Structural Genomics (Nysgxrc)

Key ref:

M.C.Bewley et al. (2006). Structures of wild-type and mutant human spermidine/spermine N1-acetyltransferase, a potential therapeutic drug target. Proc Natl Acad Sci U S A, 103, 2063-2068. PubMed id: 16455797 DOI: 10.1073/pnas.0511008103

Date:

28-Sep-05 Release date: 17-Jan-06

Protein chain

P21673  (SAT1_HUMAN) -  Diamine acetyltransferase 1 from Homo sapiens

Seq: 171 a.a.

Struc: 164 a.a.

Protein chain

P21673  (SAT1_HUMAN) -  Diamine acetyltransferase 1 from Homo sapiens

Seq: 171 a.a.

Struc: 160 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: Chains A, B: E.C.2.3.1.57 - diamine N-acetyltransferase.
• Reaction: an alkane-alpha,omega-diamine + acetyl-CoA = an N-acetylalkane- alpha,omega-diamine + CoA + H⁺

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1073/pnas.0511008103

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

PubMed id: 16455797

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

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

ABSTRACT

Spermidine/spermine N(1)-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 N(1),N(11)-bis-(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 N(epsilon)-acetyltransferase activity.

Selected figure(s)

Figure 3.
Fig. 3. Space-filling view of the two channels on opposite surfaces of the asymmetric dimer. The channels are at the dimer interface, with chain A mostly to the upper left in the view of channel 1 and to the lower right in the view of channel 2. The two views are related by a 180° rotation about the noncrystallographic 2-fold axis. Negatively charged residues that line the channels are colored red, positively charged residues are colored blue, and hydrophobic residues are colored yellow. The suffix a or b on the amino acid designations indicates whether the residue is from chain A or B. Arrows point to the parts of channel 1 that house AcCoA and polyamine. Channel 2 is occluded by residues 27-29 of chain B, which prevents polyamine but not CoA from binding.

Figure 4.
Fig. 4. Simulated-annealing omit maps showing the electron density and interactions of bound CoA and BE-3-3-3. The electron density corresponding to CoA (A and B) and BE-3-3-3 (C) is drawn as light blue chicken wire. Oxygen atoms are red spheres, and nitrogen atoms are blue spheres. (A) Interactions of CoA that occur in both channel 1 and 2 of the asymmetric dimer. Backbone nitrogens from P-loop residues G102, F103, and G104 interact with the pyrophosphate moiety of CoA. R101, Y140, R142, and R143 side chains from the same monomer are drawn in ball-and-stick representation. (B) Hydrogen bond network with chain A residues that houses the pantetheine moiety of CoA in channel 1 of the asymmetric dimer. Side-chain residues of 94 and 95 beyond C[ ]have been omitted for clarity. Hydrogen bonds are drawn as dashed lines. (C) Interactions of BE-3-3-3 in channel 1 of the asymmetric dimer. Ball-and-stick representations of residues from chain A and B of the asymmetric dimer are drawn in purple and green, respectively.

Figures were selected by an automated process.