NMR Solution Structure of a Chymotrypsin Inhibitor from the Taiwan Cobra Naja naja atra

Abstract

Abstract:The Taiwan cobra (Naja naja atra) chymotrypsin inhibitor (NACI) consists of 57 amino acids and is related to other Kunitz-type inhibitors such as bovine pancreatic trypsin inhibitor (BPTI) and Bungarus fasciatus fraction IX (BF9), another chymotrypsin inhibitor. Here we present the solution structure of NACI. We determined the NMR structure of NACI with a root-mean-square deviation of 0.37 Å for the backbone atoms and 0.73 Å for the heavy atoms on the basis of 1,075 upper distance limits derived from NOE peaks measured in its NOESY spectra. To investigate the structural characteristics of NACI, we compared the three-dimensional structure of NACI with BPTI and BF9. The structure of the NACI protein comprises one 3 10 -helix, one α-helix and one double-stranded antiparallel β-sheet, which is comparable with the secondary structures in BPTI and BF9. The RMSD value between the mean structures is 1.09 Å between NACI and BPTI and 1.27 Å between NACI and BF9. In addition to similar secondary and tertiary structure, NACI OPEN ACCESSMolecules 2013, 18 8907 might possess similar types of protein conformational fluctuations as reported in BPTI, such as Cys14-Cys38 disulfide bond isomerization, based on line broadening of resonances from residues which are mainly confined to a region around the Cys14-Cys38 disulfide bond.

Purification and Structural Study of the Voltage-Sensor Domain of the Human KCNQ1 Potassium Ion Channel

“…The TALOS+-determined secondary structure of Q1-VSD in LPPG micelles (Figure ) is dominated by α-helices (Figure A), consistent with its far-UV CD spectrum (Figure S1 of the Supporting Information). Significantly, the dihedral angles calculated with TALOS+ using the NMR chemical shift data indicate that S4 of Q1-VSD in LPPG is α-helical with no 3 10 -helical content. , …”

“…Significantly, the dihedral angles calculated with TALOS+ 33 using the NMR chemical shift data indicate that S4 of Q1-VSD in LPPG is α-helical with no 3 10 -helical content. 36 , 37 …”

“…Significantly, the dihedral angles calculated with TALOS+ 33 using the NMR chemical shift data indicate that S4 of Q1-VSD in LPPG is α-helical with no 3 10helical content. 36,37 Backbone Amide H−D Exchange of Q1-VSD. D 2 O incubation of Q1-VSD in LPPG micelles for 2 h followed by acquisition of a 1 H− 15 N TROSY spectrum provided sitespecific quantification of the degree of replacement of backbone amide protons with deuterium.…”