Structural and functional evidence for Bacillus subtilis PaiA as a novel N1-spermidine/spermine acetyltransferase.
Bacillus subtilis PaiA has been implicated in the negative control of sporulation as well as production of degradative enzymes. PaiA shares recognizable sequence homology with N-acetyltransferases, including those that can acetylate spermidine/spermine substrates. We have determined the crystal structure of PaiA in complex with CoA at 1.9 A resolution and found that PaiA is a member of the N-acetyltransferase superfamily of enzymes. Unexpectedly, we observed the binding of an oxidized CoA dimer in the active site of PaiA, and the structural information suggests the substrates of the enzyme could be linear, positively charged compounds. Our biochemical characterization is also consistent with this possibility, since purified PaiA possesses N1-acetyltransferase activity toward polyamine substrates including spermidine and spermine. Further, conditional overexpression of PaiA in bacteria results in increased acetylation of endogenous spermidine pools. Thus, our structural and biochemical analyses indicate that PaiA is a novel N-acetyltransferase capable of acetylating both spermidine and spermine. In this way, the pai operon may function in regulating intracellular polyamine concentrations and/or binding capabilities. In addition to preventing toxicity due to polyamine excess, this function may also serve to regulate expression of certain bacterial gene products such as those involved in sporulation.
Forouhar
Farhad
F
Department of Biological Sciences, Northeast Structural Genomics Consortium, Columbia University, New York, New York 10027, USA.
Lee
In-Sun
IS
Vujcic
Jelena
J
Vujcic
Slavoljub
S
Shen
Jianwei
J
Vorobiev
Sergey M
SM
Xiao
Rong
R
Acton
Thomas B
TB
Montelione
Gaetano T
GT
Porter
Carl W
CW
Tong
Liang
L
D000123:Acetyltransferases / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000378:metabolism*; D002384:Catalysis; D002412:Cations; D002850:Chromatography, Gel; D018360:Crystallography, X-Ray; D019281:Dimerization; D004229:Dithiothreitol / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010100:Oxygen / Q000737:chemistry; D011073:Polyamines / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D000099228:Diamine N-Acetyltransferase
D000123:Acetyltransferases; D002412:Cations; D004229:Dithiothreitol; D010100:Oxygen; D011073:Polyamines; D000099228:Diamine N-Acetyltransferase