PMID: 26110759

Authors:

Glaza P, Osipiuk J, Wenta T, Zurawa-Janicka D, Jarzab M, Lesner A, Banecki B, Skorko-Glonek J, Joachimiak A, Lipinska B

Title:

Structural and Functional Analysis of Human HtrA3 Protease and Its Subdomains.

Journal:

PLoS One. 2015 Jun 25;10(6):e0131142. doi: 10.1371/journal.pone.0131142., eCollection 2015.

Abstract:

Human HtrA3 protease, which induces mitochondria-mediated apoptosis, can be a tumor suppressor and a potential therapeutic target in the treatment of cancer. However, there is little information about its structure and biochemical properties. HtrA3 is composed of an N-terminal domain not required for proteolytic activity, a central serine protease domain and a C-terminal PDZ domain. HtrA3S, its short natural isoform, lacks the PDZ domain which is substituted by a stretch of 7 C-terminal amino acid residues, unique for this isoform. This paper presents the crystal structure of the HtrA3 protease domain together with the PDZ domain (DeltaN-HtrA3), showing that the protein forms a trimer whose protease domains are similar to those of human HtrA1 and HtrA2. The DeltaN-HtrA3 PDZ domains are placed in a position intermediate between that in the flat saucer-like HtrA1 SAXS structure and the compact pyramidal HtrA2 X-ray structure. The PDZ domain interacts closely with the LB loop of the protease domain in a way not found in other human HtrAs. DeltaN-HtrA3 with the PDZ removed (DeltaN-HtrA3-DeltaPDZ) and an N-terminally truncated HtrA3S (DeltaN-HtrA3S) were fully active at a wide range of temperatures and their substrate affinity was not impaired. This indicates that the PDZ domain is dispensable for HtrA3 activity. As determined by size exclusion chromatography, DeltaN-HtrA3 formed stable trimers while both DeltaN-HtrA3-DeltaPDZ and DeltaN-HtrA3S were monomeric. This suggests that the presence of the PDZ domain, unlike in HtrA1 and HtrA2, influences HtrA3 trimer formation. The unique C-terminal sequence of DeltaN-HtrA3S appeared to have little effect on activity and oligomerization. Additionally, we examined the cleavage specificity of DeltaN-HtrA3. Results reported in this paper provide new insights into the structure and function of DeltaN-HtrA3, which seems to have a unique combination of features among human HtrA proteases.