Probably plays an important role in the regulation of erythrocyte shape and mechanical properties. Oligomer. Interacts with the cytoplasmic domain of SLC4A1/band 3 anion transport protein. Cytoplasmic surface of erythrocyte membranes. Both cAMP-dependent kinase (CAPK) and another kinase present in the red-blood cells seem to be able to phosphorylate EPB42. The disease is caused by variants affecting the gene represented in this entry. The substitution of an Ala for a Cys in the active site may be responsible for the lack of transglutaminase activity of band 4.2. Major isoform. Belongs to the transglutaminase superfamily. Transglutaminase family.