کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1926830 1536484 2008 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
X-ray studies on ternary complexes of maltodextrin phosphorylase
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی زیست شیمی
پیش نمایش صفحه اول مقاله
X-ray studies on ternary complexes of maltodextrin phosphorylase
چکیده انگلیسی

We report crystal structures of ternary complexes of maltodextrin phosphorylase with natural oligosaccharide and phosphate mimicking anions: nitrate, sulphate and vanadate. Electron density maps obtained from crystals grown in presence of Al(NO3)3 show a nitrate ion instead of the expected AlF4- in the catalytic site. The trigonal NO3- is coplanar with the Arg569 guanidinium group and mimics three of the four oxygen atoms of phosphate. The ternary complex with sulphate shows a partial occupancy of the anionic site. The low affinity of the sulphate ion, observed when the α-glucosyl substrate is present in the catalytic channel, is ascribed to restricted space for the anion. Even lower occupancy is observed for the larger vanadate anion. The Malp/G5/VO43- structure shows the partial occupancy of the oligosaccharide and the dislocation of the 380’s loop. This has been attributed to the formation of oligosaccharide vanadate derivatives (confirmed by capillary electrophoresis) that reduces their effective concentration. The difficulty to trap a ternary complex mimicking the ground state has been correlated to the apparent lower affinity that natural substrates show regarding the intermediates of the enzymatic reaction.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Archives of Biochemistry and Biophysics - Volume 471, Issue 1, 1 March 2008, Pages 11–19
نویسندگان
, , , , ,