Major Histocompatibility Complex Binding Protein 1 (MBP1)

Members of the ZAS family, such as ZAS1 (HIVEP1), are large proteins that contain a ZAS domain, a modular protein structure consisting of a pair of C2H2 zinc fingers with an acidic-rich region and a serine/threonine-rich sequence. These proteins bind specific DNA sequences, including the kappa-B motif (GGGACTTTCC), in the promoters and enhancer regions of several genes and viruses, including human immunodeficiency virus (HIV).

ZNF40, a protein that binds to these sequences, has a molecular mass of 298 kD and contains 2 widely separated zinc finger binding domains, each of which binds to the same DNA sequence. This protein has variously been known as HIVEP1, MBP1, and PRDII-BF1.