LOCALIZATION OF TRANSGLUTAMINASE-REACTIVE GLUTAMINE RESIDUES IN BOVINE OSTEOPONTIN

Here we report the identification of two translgutaminase-reactive glu tamines (Gln-34 and Gln-36) in bovine osteopontin (OPN). Sequence alig nment revealed that these glutamines are conserved in all known OPN se quences, indicating a functional importance of this region of the prot ein. Furthermore, immunological analysis of bovine bone demonstrated t hat OPN is present in high-molecular-mass complexes in vivo. These fin dings support the functional aspects of a transglutaminase-catalysed c ross-linking of OPN in facilitating cellular attachment and tissue cal cification.