| Structural highlights
Function
BPSA_THEKO Involved in the biosynthesis of branched-chain polyamines, which support the growth of thermophiles under high-temperature conditions. Catalyzes the sequential condensation of spermidine with the aminopropyl groups of decarboxylated S-adenosylmethionines to produce N(4)-bis(aminopropyl)spermidine via N(4)-aminopropylspermidine. Can also use spermine to produce N(4)-aminopropylspermine.[1]
Publication Abstract from PubMed
Branched-chain polyamine synthase (BpsA) catalyzes sequential aminopropyl transfer from the donor, decarboxylated S-adenosylmethionine (dcSAM), to the acceptor, linear-chain polyamine, resulting in the production of a quaternary-branched polyamine via tertiary branched polyamine intermediates. Here, we analyzed the catalytic properties and X-ray crystal structure of Tth-BpsA from Thermus thermophilus and compared them with those of Tk-BpsA from Thermococcus kodakarensis, which revealed differences in acceptor substrate specificity and C-terminal structure between these two enzymes. To investigate the role of the C-terminal flexible region in acceptor recognition, a region (QDEEATTY) in Tth-BpsA was replaced with that in Tk-BpsA (YDDEESSTT) to create chimeric Tth-BpsA C9, which showed a severe reduction in catalytic efficiency toward N(4) -aminopropylnorspermidine, but not toward N(4) -aminopropylspermidine, mimicking Tk-BpsA substrate specificity. Tth-BpsA C9 Tyr(346) and Thr(354) contributed to discrimination between tertiary branched-chain polyamine substrates, suggesting that the C-terminal region of BpsA recognizes acceptor substrates. Liquid chromatography-tandem mass spectrometry analysis on a Tk-BpsA reaction mixture with dcSAM revealed two aminopropyl groups bound to two of five aspartate/glutamate residues (Glu(339) , Asp(342) , Asp(343) , Glu(344) , and Glu(345) ) in the C-terminal flexible region. Mutating each of these five amino acid residues to asparagine/glutamine resulted in a slight decrease in activity. The quadruple mutant D342N/D343N/E344Q/E345Q exhibited a severe reduction in catalytic efficiency, suggesting that these aspartate/glutamate residues function to receive aminopropyl chains. In addition, the X-ray crystal structure of the Tk-BpsA ternary complex bound to N(4) -bis(aminopropyl)spermidine revealed that Asp(126) and Glu(259) interacted with the aminopropyl moiety in N(4) -aminopropylspermidine.
The C-terminal flexible region of branched-chain polyamine synthase facilitates substrate specificity and catalysis.,Hidese R, Toyoda M, Yoshino KI, Fukuda W, Wihardja GA, Kimura S, Fujita J, Niitsu M, Oshima T, Imanaka T, Mizohata E, Fujiwara S FEBS J. 2019 Jun 4. doi: 10.1111/febs.14949. PMID:31162806[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Okada K, Hidese R, Fukuda W, Niitsu M, Takao K, Horai Y, Umezawa N, Higuchi T, Oshima T, Yoshikawa Y, Imanaka T, Fujiwara S. Identification of a novel aminopropyltransferase involved in the synthesis of branched-chain polyamines in hyperthermophiles. J Bacteriol. 2014 May;196(10):1866-76. doi: 10.1128/JB.01515-14. Epub 2014 Mar 7. PMID:24610711 doi:http://dx.doi.org/10.1128/JB.01515-14
- ↑ Hidese R, Toyoda M, Yoshino KI, Fukuda W, Wihardja GA, Kimura S, Fujita J, Niitsu M, Oshima T, Imanaka T, Mizohata E, Fujiwara S. The C-terminal flexible region of branched-chain polyamine synthase facilitates substrate specificity and catalysis. FEBS J. 2019 Jun 4. doi: 10.1111/febs.14949. PMID:31162806 doi:http://dx.doi.org/10.1111/febs.14949
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