Two‐dimensional nuclear Overhauser enhancement (NOESY) spectra of labile protons were recorded in H2O solutions of a protein and of a DNA duplex, using a modification of the standard NOESY experiment ...with all three 90° pulses replaced by jump‐and‐return sequences. For the protein as well as the DNA fragment the strategically important spectral regions could be recorded with good sensitivity and free of artifacts. Using this procedure, sequence‐specific assignments were obtained for the imino protons, C2H of adenine, and C4NH2 of cytosine in a 23‐base‐pair DNA duplex which includes the 17‐base‐pair OR3 repressor binding site of bacteriophage λ. Based on comparison with previously published results on the isolated OR3 binding site, these data were used for a study of chain termination effects on the chemical shifts of imino proton resonances of DNA duplexes.
Sequence‐specific assignments of the
1
H‐nuclear magnetic resonance (NMR) spectra of the cardiotoxins CTXIIa and CTXIIb from
Naja mossambica mossambica
were obtained using two‐dimensional NMR ...experiments at 500 MHz and the independently determined amino acid sequences. Assignments were obtained from data at 25°C and 45°C for all but one back bone proton of the 60 residues in each protein. Complete or partial assignments are also reported for the side‐chain protons. These assignments supercede those published previously for the toxin preparation V
II
2 Hosur, R. V., Wider, G. & Wüthrich K. (1983)
Eur. J. Biochem. 130
, 497–508. The
1
H/
2
H‐exchange kinetics were measured in
2
H
2
O at 20°C for the amide protons and the N‐terminal amino group. These and additional NMR data enabled the determination of the secondary structure in aqueous solution, which is virtually identical in CTXIIa and CTXIIb. Both proteins contain a short double‐stranded antiparallel β‐sheet comprising the residues 2–4 and 11–13, and a triple‐stranded antiparallel β‐sheet consisting of the residues 20–26, 35–39, and 49–55. The two peripheral strands of the triple‐stranded β‐structure were found to be connected by a right‐handed cross‐over, and the locations of several tight turns were also identified.
High‐resolution phase‐sensitive two‐dimensional proton nuclear magnetic resonance was used to monitor the preparation by high‐performance liquid chromatography of homogeneous proteins from the venom ...of Naja mossambica mossambica. This resulted in the characterization of a heterogeneous protein preparation VII2, which had been used in earlier structural studies by NMR, as well as a homogeneous protein CTXIIb and a nearly homogeneous protein fraction CTXIIa, which are now both subject to further investigations of their solution conformations.
Sequence‐specific assignments of the 1H‐nuclear magnetic resonance (NMR) spectra of the cardiotoxins CTXIIa and CTXIIb from Naja mossambica mossambica were obtained using two‐dimensional NMR ...experiments at 500 MHz and the independently determined amino acid sequences. Assignments were obtained from data at 25°C and 45°C for all but one back bone proton of the 60 residues in each protein. Complete or partial assignments are also reported for the side‐chain protons. These assignments supercede those published previously for the toxin preparation VII2 Hosur, R. V., Wider, G. & Wüthrich K. (1983) Eur. J. Biochem. 130, 497–508. The 1H/2H‐exchange kinetics were measured in 2H2O at 20°C for the amide protons and the N‐terminal amino group. These and additional NMR data enabled the determination of the secondary structure in aqueous solution, which is virtually identical in CTXIIa and CTXIIb. Both proteins contain a short double‐stranded antiparallel β‐sheet comprising the residues 2–4 and 11–13, and a triple‐stranded antiparallel β‐sheet consisting of the residues 20–26, 35–39, and 49–55. The two peripheral strands of the triple‐stranded β‐structure were found to be connected by a right‐handed cross‐over, and the locations of several tight turns were also identified.
PDF