The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Identification of an isoaspartyl linkage formed upon deamidation of bovine calbindin D9k and structural characterization by 2D 1H NMR.

Preparations of recombinant bovine calbindin D9k (r-calbindin) that appear homogeneous on SDS electrophoresis gels have been shown by isoelectric focusing to be mixtures of proteins differing in net charge. The production of two isoforms with increased negative charge occurs during a routine urea denaturation step and can be effectively suppressed by replacing this procedure with thermal denaturation. The two isoforms have been separated from the native protein by DEAE-Sephacel ion-exchange chromatography. Amino acid sequencing of tryptic peptide fragments and two-dimensional (2D) 1H NMR studies establish that the isoforms correspond to calbindin D9k deamidated at Asn56 and that the major product has an isoaspartate (beta-linked peptide) residue at this position. The minor deamidated component is found to have a normal Asp-Gly alpha-linkage. A detailed analysis of proton chemical shifts, phi backbone dihedral angles, and nuclear Overhauser effects indicates that the global conformation of r-calbindin is not perturbed upon deamidation and that all elements of secondary structure are intact. The Asp56 form is nearly identical with the intact protein, whereas the structure of the iso-Asp56 form is perturbed, predominantly in the polypeptide segment Lys55-Asp58. These studies demonstrate that 2D 1H NMR techniques can be used to identify and quantitate the two isoforms produced upon deamidation of a protein and to assess changes in the local and global conformation.[1]

References

  1. Identification of an isoaspartyl linkage formed upon deamidation of bovine calbindin D9k and structural characterization by 2D 1H NMR. Chazin, W.J., Kördel, J., Thulin, E., Hofmann, T., Drakenberg, T., Forsén, S. Biochemistry (1989) [Pubmed]
 
WikiGenes - Universities