MAST4 Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. 5 isoforms of the human protein are produced by alternative splicing. Human protein kinases make up a large superfamily of homologous proteins, which are related by virtue of their kinase domains.MAST4 locates on human chromosome 5q13. The MAST4 cDNA is 7587 base pairs in length and encodes a putative protein of 2435 amino acids which contains a serine/threonine kinase domain and a PDZ domain. MAST4 protein has 64%, 63%, 59% and 39% identical aminoacid residues with MAST1, MAST2, MAST3 and MASTL respectively. RT-PCR analysis revealed relatively high expression level of MAST4 in most normal human tissues, with an exception of in testis, small intestine, colon and peripheral blood leukocyte.