THE INTERACTION OF ARENICIN-1 WITH C3B COMPLEMENT PROTEIN

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Introduction. The coevolution and colocalization of complement system and antimicrobial peptides (AMPs) give the opportunity to assume the existence of close interactions between different components of these systems. There are some data about such interactions and consequences of such interplay, including complement modulation [1-5]. But they are not so numerous and some of them are rather contradictory. The earlier results of our investigations confirm the literature data about the interactions between C1q and human defensins, tachyplesin-1, arenicin-1 (Ar-1), protegrin-1 form complexes with C1q directly [6]. We also showed that different AMPs possess modulator activity on complement depending on peptide concentrations; in particular, Ar-1 influenced the classical and alternative complement activation pathways [7]. It is likely that peptide interacts with the central complement component - C3, because we observed total inhibition of two complement pathways and their common point is C3 protein. In this study we investigated the binding of Ar-1 with complement protein C3b, the fragment of activated C3 protein. Material and methods. The data about the interaction of C3b with Ar-1 were obtained utilizing surface plasmon resonance (SPR) on Biacore™ X100. The series of experiments were performed on CM4 sensor chip with C3b upon addition of Ar-1 (7.8-500 nM) to the analytical cells. We calculated some models of C3c fragment and Ar-1 interaction using methods for molecular docking (Rosetta, FlexPepDock algorithm) and molecular dynamics (AMBER). Results and discussion. We obtained the data from SPR analisys that describe heterogeneous ligand binding. It might mean that there are two types of interaction sites with high affinity (Kd = 7 nM) and with low affinity (Kd = 92 μM). We also calculated some models of C3c fragment (Chain D (328-535), PDB ID: 2qki) and Ar-1 interaction. It appeared that there are some common sites on C3c fragment for compstatin, well-described peptide inhibitor of C3, and Ar-1 binding (Fig. 1). C3c (Chain D 328-535) - Ar-1 complex is stabilized by hydrogen bonds and salt bridges. These facts should be examined carefully to construct peptide molecules derived from these AMPs that will have strong modulatory properties depending not only the concentration but also other important parameters. The advantage of this kind of molecules is in their relative stability that is also very important for the design of new complement regulators for treating complement-related diseases.

About the authors

E S Umnyakova

Institute of Experimental Medicine, Saint Petersburg

I A Krenev

Saint Petersburg State University

S V Legkovoy

Saint Petersburg State University

A V Sokolov

Institute of Experimental Medicine, Saint Petersburg

O N Rogacheva

Saint Petersburg State University

T V Ovchinnikova

M.M. Shemyakin and Yu.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow

V N Kokryakov

Institute of Experimental Medicine, Saint Petersburg; Saint Petersburg State University

M N Berlov

Institute of Experimental Medicine, Saint Petersburg

References

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