Crystal structure of Smolstatin – protease inhibitor from the myxozoan parasite Sphaerospora molnari

P. Havlíčková¹, B. Kaščáková¹, I. Kutá Smatanová¹, D. Sojka², P. Bartošová-Sojková²

¹Department of Chemistry, Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic

²Institute of Parasitology, Biology Centre of the CAS, Ceske Budejovice, Czech Republic

bartosova@paru.cas.cz

The cystatin superfamily is a large group of cysteine protease inhibitors (including type 1 cystatins – stefins, type 2 cystatins – true cystatins and type 3 cystatins – kininogens), present in various organisms. Parasite cystatins are involved in the active parasitism in the host by supressing host immune responses. Thus, cystatins are critical for the interactions between host and parasite during the infection [1, 2].

Here, we structurally characterized stefin Smolstatin from Sphaerospora molnari, which is a myxozoan parasite of common carp Cyprinus carpio. From evolutionary point of view, myxozoans are parasites that stand at the base of the metazoan evolution, therefore structural information can bring insights into the evolution of the cystatin superfamily as well as it can contribute to the aquaculture field for studying host- parasite interactions [3]. Smolstatin is a 13.5 kDa large single domain protein, which consists of typical cystatin-like domain, but unlikely for stefins, it also carries a signal peptide.

Smolstatin was recombinantly produced, purified and crystallized using sitting drop vapour diffusion technique. Diffraction data were collected on BL14.1 at the BESSY II electron storage ring operated by the Helmholtz-Zentrum Berlin [4]. Smolstatin crystallized as a domain swapped dimer. The crystal structure was determined by molecular replacement, refined and deposited to the PDB database under the accession code 8and.   

1. Hartmann, S. & Lucius, R. Int. J. Parasitol. 33, (2003), 1291-19203.

2. Klotz, C. et al. In Cysteine Proteases of Pathogenic Organisms. Advances in Experimental Medicine and Biology, edited by Robinson M. W., Dalton J. P. (Boston: Springer), 2011, Volume 712.

3. Bartošová-Sojková et al. Biology (Basel). 10, (2021), 110.

4. Mueller, U. et al. Eur. Phys. J. Plus. 130, (2015), 141-150.

This research was supported by GAČR 21-16565S, GAJU 106/2021/P and ERDF No. CZ.02.1.01/0.0/0.0/15_003/000041.