Transglutaminase catalyses the modification of glutamine side chains in the C-terminal region of bovine β-lactoglobulin

Abstract

The transglutaminase-catalysed incorporation of primary amines (putrescine and monodansylcadaverine) into bovine β-lactoglobulin has been studied. In the presence of 1 mM-dithiothreitol between 1 and 2 mol of amine can be incorporated per mol of β-lactoglobulin subunit. There is very little incorporation of amines in the absence of reducing agent. By isolating and sequencing the modified peptides, the sites of modification have been identified as Gln-159 (preferred) and Gln-155. C.d. has been used to study the structure of β-lactoglobulin over a range of pH values and in the presence or absence of dithiothreitol. The results are discussed in terms of the X-ray-crystallographically determined structure of β-lactoglobulin.