Delineation of the IGF-II C domain elements involved in binding and activation of the IR-A, IR-B and IGF-IR.

Objective: Human insulin-like growth factor-I and -II (IGF-I and -II) ligands share a high degree of sequence and structural homology. Despite their similarities, IGF-I and IGF-II exhibit differential receptor binding and activation characteristics. The C domains of IGF-I and IGF-II are the primary determinants of binding specificity to the insulin-like growth factor I receptor (IGF-IR), insulin receptor exon 11- (IR-A) and exon 11+ (IR-B) isoforms.

Novel insights into the biotin carboxylase domain reactions of pyruvate carboxylase from Rhizobium etli.

The catalytic mechanism of the MgATP-dependent carboxylation of biotin in the biotin carboxylase domain of pyruvate carboxylase from R. etli (RePC) is common to the biotin-dependent carboxylases. The current site-directed mutagenesis study has clarified the catalytic functions of several residues proposed to be pivotal in MgATP-binding and cleavage (Glu218 and Lys245), HCO(3)(-) deprotonation (Glu305 and Arg301), and biotin enolization (Arg353).

Insights into the mechanism and regulation of pyruvate carboxylase by characterisation of a biotin-deficient mutant of the Bacillus thermodenitrificans enzyme.

Pyruvate carboxylase is a biotin-dependent enzyme in which the biotin is carboxylated by a putative carboxyphosphate intermediate that is formed in a reaction between ATP and bicarbonate. The resultant carboxybiotin then transfers its carboxyl group to pyruvate to form oxaloacetate. In the Bacillus thermodenitrificans enzyme the biotin is covalently attached to K1112.

An investigation of the ligand binding properties and negative cooperativity of soluble insulin-like growth factor receptors.

To investigate the interaction of the insulin-like growth factor (IGF) ligands with the insulin-like growth factor type 1 receptor (IGF-1R), we have generated two soluble variants of the IGF-1R. We have recombinantly expressed the ectodomain of IGF-1R or fused this domain to the constant domain from the Fc fragment of mouse immunoglobulin. The ligand binding properties of these soluble IGF-1Rs for IGF-I and IGF-II were investigated using conventional ligand competition assays and BIAcore biosensor technology.

Domain architecture of pyruvate carboxylase, a biotin-dependent multifunctional enzyme.

Biotin-dependent multifunctional enzymes carry out metabolically important carboxyl group transfer reactions and are potential targets for the treatment of obesity and type 2 diabetes. These enzymes use a tethered biotin cofactor to carry an activated carboxyl group between distantly spaced active sites. The mechanism of this transfer has remained poorly understood.