ProteaImmun is now offering besides HtrA1 also HtrA3 and HtrA4 which allows detailed studies of the structure and function of these proteases.

HtrA3
HtrA3 belongs to the High-Temperature Requirement Factor A family that is well conserved from bacteria to humans. In bacteria, HtrA proteins have at high temperatures, a serine protease activity that allows the degradation of misfolded proteins and, at low temperatures, a molecular chaperon activity. In mammals four homologues have been reported (HtrA1, HtrA2, HtrA3 and HtrA4). HtrA1 and HtrA3 have very similar protein domain structure, whereas HtrA2 is different.

HtrA3 is expressed and secreted by a wide range of tissues although at different levels. It has a very high expression in heart, ovary, bladder and placenta and a lower one in colon, lung and kidney. HtrA3 is a pregnancy-related serine protease involved in placental development and function in mouse and human. It has also been shown to modulate TGF-β signaling and IGF/IGFBP systems which are critical regulators for placental development. Studies have also shown that expression of HtrA3 is dramatically decreased in endometrial and ovarian cancers. Recombinant HtrA3 allows detailed studies of the structure and function of this protease. The enzyme is used to screen for inhibitors and to characterize inhibitor actions. Recombinant HtrA3 can also serve as standard in enzymatic and immunochemical assays.

HtrA4
HtrA4 is a secreted human serine protease supposed to form oligomers of identical protein chains as revealed by X-ray analysis for the bacterial HtrA protein DegP. Polypeptide chains of human HtrA4 consist of several domains: An N-terminal insulin-like growth factor domain is followed by a Kazal-type serine protease inhibitor domain, a linker region, a trypsin-like protease domain and a PDZ domain. The function of HtrA4 is a probable serine protease. No information is available yet on physiological substrates or interacting proteins. Recombinant HtrA4 allows detailed studies of the structure and function of this protease. The enzyme is used to screen for inhibitors and to characterize inhibitor actions. Recombinant HtrA4 can also serve as standard in enzymatic and immunochemical assays.