کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1925958 1536428 2010 7 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Comparison of solution and crystal properties of Co(II)–substituted human carbonic anhydrase II
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی زیست شیمی
پیش نمایش صفحه اول مقاله
Comparison of solution and crystal properties of Co(II)–substituted human carbonic anhydrase II
چکیده انگلیسی

The visible absorption of crystals of Co(II)–substituted human carbonic anhydrase II (Co(II)–HCA II) were measured over a pH range of 6.0–11.0 giving an estimate of pKa 8.4 for the ionization of the metal-bound water in the crystal. This is higher by about 1.2 pKa units than the pKa near 7.2 for Co(II)–CA II in solution. This effect is attributed to a nonspecific ionic strength effect of 1.4 M citrate in the precipitant solution used in the crystal growth. A pKa of 8.3 for the aqueous ligand of the cobalt was measured for Co(II)–HCA II in solution containing 0.8 M citrate. Citrate is not an inhibitor of the catalytic activity of Co(II)–HCA II and was not observed in crystal structures. The X-ray structures at 1.5–1.6 Å resolution of Co(II)–HCA II were determined for crystals prepared at pH 6.0, 8.5 and 11.0 and revealed no conformational changes of amino-acid side chains as a result of the use of citrate. However, the studies of Co(II)–HCA II did reveal a change in metal coordination from tetrahedral at pH 11 to a coordination consistent with a mixed population of both tetrahedral and penta-coordinate at pH 8.5 to an octahedral geometry characteristic of the oxidized enzyme Co(III)–HCA II at pH 6.0.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Archives of Biochemistry and Biophysics - Volume 502, Issue 1, 1 October 2010, Pages 53–59
نویسندگان
, , , , , ,