کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8291987 | 1536478 | 2008 | 10 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Structure of the two-subsite β-d-xylosidase from Selenomonas ruminantium in complex with 1,3-bis[tris(hydroxymethyl)methylamino]propane
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کلمات کلیدی
موضوعات مرتبط
علوم زیستی و بیوفناوری
بیوشیمی، ژنتیک و زیست شناسی مولکولی
زیست شیمی
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چکیده انگلیسی
The three-dimensional structure of the catalytically efficient β-xylosidase from Selenomonas ruminantium in complex with competitive inhibitor 1,3-bis[tris(hydroxymethyl)methylamino]propane (BTP) was determined by using X-ray crystallography (1.3 Ã
resolution). Most H bonds between inhibitor and protein occur within subsite â1, including one between the carboxyl group of E186 and an N group of BTP. The other N of BTP occupies subsite +1 near K99. E186 (pKa 7.2) serves as catalytic acid. The pH (6-10) profile for 1/Ki(BTP) is bell-shaped with pKa's 6.8 and 7.8 on the acidic limb assigned to E186 and inhibitor groups and 9.9 on the basic limb assigned to inhibitor. Mutation K99A eliminates pKa 7.8, strongly suggesting that the BTP monocation binds to the dianionic enzyme D14âE186â. A sedimentation equilibrium experiment estimates a Kd ([dimer]2/[tetramer]) of 7Â ÃÂ 10â9Â M. Similar kcat and kcat/Km values were determined when the tetramer/dimer ratio changes from 0.0028 to 26 suggesting that dimers and tetramers are equally active forms.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Archives of Biochemistry and Biophysics - Volume 474, Issue 1, 1 June 2008, Pages 157-166
Journal: Archives of Biochemistry and Biophysics - Volume 474, Issue 1, 1 June 2008, Pages 157-166
نویسندگان
Joseph S. Brunzelle, Douglas B. Jordan, Darrell R. McCaslin, Andrzej Olczak, Zdzislaw Wawrzak,