SOLUTION STRUCTURE OF THE GRANULAR STARCH BINDING DOMAIN OF GLUCOAMYLASE FROM ASPERGILLUS NIGER BY NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY

摘要: The solution structure of the granular starch binding domain (SBD) glucoamylase 1 fromAspergillus nigerhas been determined by heteronuclear multidimensional nuclear magnetic resonance spectroscopy and simulated annealing. A total 1092 Overhauser enhance ment-derived1H-1H distance constraints, 137 dihedral constraints 86 hydrogen bond were incorporated into an X-PLOR annealing refinement protocol. family calculated structures shows a well defined β-sheet consisting one parallel six antiparallel pairs β-strands which forms open-sided β-barrel. root-mean-square deviation (rmsd) 53 individual to average for backbone atoms residues excluding N terminus two mobile loops is 0.57(±0.10) while rmsd in 0.45(±0.08) A. Structural features SBD are compared X-ray crystal homologous cyclodextrin glycosyltransferase (CGTase) free bound forms. Titration studies with ligands, maltoheptaose β-cyclodextrin, show existence sites. Examination tertiary these sites be at end molecule on opposite faces. majority showing largest1H and15N chemical shift changes located loop regions. Many implicated binding, based changes, similar location previously identified site CGTase. Overall, small indicating that does not undergo large conformational upon ligand binding.