The red cell membrane contains calmodulin-regulated crosslinking and proteolytic activity.

Abstract

Several different forms of transglutaminase (TGase) have been documented and these forms may coexist in the same cell. Cytosolic erythrocyte transglutaminases active at millimolar calcium concentrations have been well described. This report discusses membrane-associated erythrocyte TGase activity which can crosslink substrates at micromolar calcium concentrations in the presence of calmodulin (CaM). This TGase activity coisolates with a 1 M NaCl extraction of cytoskeletal components and is purified by CaM affinity chromatography. The EGTA eluate from the affinity chromatography displays TGase activity at ten times that of the initial hemolysate. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of this eluate demonstrates two bands of 68,000 and 72,000 daltons. TGase crosslinking of fibronectin, fibrinogen, and membrane cytoskeletal substrates was associated with substrate degradation and could be inhibited competitively by putrescine. Similarities of this TGase to those of the platelet and smooth muscle membrane-associated TGases are explored. CaM-calcium regulated, membrane-associated erythrocyte TGases may play a role in membrane-cytoskeletal interactions.