期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 102, 期 39, 页码 13819-13824出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0505726102
关键词
pyridoxal phosphate; radical mechanism; S-adenosylmethionine
资金
- NCRR NIH HHS [P41 RR007707, RR07707] Funding Source: Medline
- NIDDK NIH HHS [DK28607, R01 DK028607] Funding Source: Medline
The x-ray crystal structure of the pyrid oxa 1-5'-phosphate (PLP), S-adenosyl-L-methionine (SAM), and [4Fe-4S]-dependent lysine-2,3-aminomutase (LAM) of Clostridium subterminale has been solved to 2.1-angstrom resolution by single-wavelength anomalous dispersion methods on a L-selenomethionine-substituted complex of LAM with [4Fe-4S](2+), PLP, SAM, and L-alpha-lysine, a very close analog of the active Michaelis complex. The unit cell contains a dimer of hydrogen-bonded, domain-swapped dimers, the subunits of which adopt a fold that contains all three cofactors in a central channel defined by six beta/alpha structural units. Zinc coordination links the domain-swapped dimers. In each subunit, the solvent face of the channel is occluded by an N-terminal helical domain, with the opposite end of the channel packed against the domain-swapped subunit. Hydrogen-bonded ionic contacts hold the external aldimine of PLP and L-alpha-lysine in position for abstraction of the 3-pro-R hydrogen of lysine by C5' of SAM. The structure of the SAM/[4Fe4S] complex confirms and extends conclusions from spectroscopic studies of LAM and shows selenium in Se-adenosyl-L-selenomethionine poised to ligate the unique iron in the [4Fe-4S] cluster upon electron transfer and radical formation. The chain fold in the central domain is in part analogous to other radical-SAM enzymes.
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