Crystal structure of globin domain of AfGcHK histidine kinase

T. Skálová¹, P. Kolenko^1,2, M. Stráňava³, J. Bláha³, J. Dohnálek¹, M. Martínková³

¹ Institute of Biotechnology CAS, v.v.i., Biocev, 252 50 Vestec, Czech Republic

² Department of Solid State Engineering, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Brehova 7, 115 19 Praha 1, Czech Republic

³ Department of Biochemistry, Faculty of Science, Charles University, Hlavova (Albertov) 2030/8, Prague 2, 128 43, Czech Republic

t.skalova@gmail.com

Histidine kinase from Anaeromyxobacter sp. Fw109-5, denoted as AfGcHK, is a homodimer, each chain containing two distinct domains. The N-terminal domain is a heme-binding globin domain and the C-terminal domain is the active domain of the histidine kinase. The globin domain regulates the activity of the histidine kinase as an oxygen sensor: oxygen binding to the globin domain heme has structural and dynamic effect on both domains of the histidine kinase.

            Here we present the first crystal structures of the isolated globin domain of AfGcHK – the structure with cyanide bound to the heme (PDB code 5OHE) and the structure of the partially reduced globin (PDB code 5OHF)¹. The protein shows relatively large structural changes upon its reduction.

The protein was crystallized and red wedge-shaped crystals with dimensions up to 80 x 80 x 300 µm were obtained. The unit cell has a rather large size (unit cell parameters 78 Å, 78 Å, 441 Å, space group P4₁2₁2) and the asymmetric unit contains eight chains A-H (four dimers AB, CD, EF and GH) of the globin domain. This is not advantageous during structure solution; however, it is convenient for stability of the crystal during reduction as only dimer GH of the four dimers in the asymmetric unit shows changes when a reduction agent is added. Ca. 30% of the protein chain G was found in two alternative positions connected with the change of the heme position and with the loss of its ligand. Neighboring parts of chain H are changed too. The other three globin dimers are intact and form a scaffold in the crystal so that this observation in chain G was possible without destroying the crystal.

1. M. Stranava, P. Man, T. Skálová, P. Kolenko, J. Blaha, V. Fojtikova, V. Martínek, J. Dohnálek, A. Lengalova, M. Rosůlek, T. Shimizu, M. Martínková. Coordination and redox state-dependent structural changes of the heme-based oxygen sensor AfGcHK associated with intraprotein signal transduction, J. Biol. Chem. 2017, 292 (51), 20921-20935.

This work was supported by Grant Agency of the Czech Republic Grant 15-19883S, Ministry of Education, Youth, and Sports of the Czech Republic Grant LM2015043 CIISB, Biocev -Crystallization, Diffraction and LTC17065 in frame of COST Action CA15126 MOBIEU. This work was also partly funded by Instruct, part of the European Strategy Forum on Research Infrastructures (ESFRI) and supported by national member subscriptions.