*Article* **Porin from Marine Bacterium** *Marinomonas primoryensis* **KMM 3633T: Isolation, Physico-Chemical Properties, and Functional Activity**

**Olga D. Novikova 1,\*, Valentina A. Khomenko 1, Natalia Yu. Kim 1, Galina N. Likhatskaya 1, Lyudmila A. Romanenko 1, Ekaterina I. Aksenova 2, Marina S. Kunda 2, Natalia N. Ryzhova 2, Olga Yu. Portnyagina 1, Tamara F. Solov'eva <sup>1</sup> and Olga L. Voronina 2,\***


Academic Editor: Maksymilian Chruszcz Received: 26 May 2020; Accepted: 3 July 2020; Published: 8 July 2020

**Abstract:** *Marinomonas primoryensis* KMM 3633T, extreme living marine bacterium was isolated from a sample of coastal sea ice in the Amursky Bay near Vladivostok, Russia. The goal of our investigation is to study outer membrane channels determining cell permeability. Porin from *M. primoryensis* KMM 3633T (MpOmp) has been isolated and characterized. Amino acid analysis and whole genome sequencing were the sources of amino acid data of porin, identified as Porin\_4 according to the conservative domain searching. The amino acid composition of MpOmp distinguished by high content of acidic amino acids and low content of sulfur-containing amino acids, but there are no tryptophan residues in its molecule. The native MpOmp existed as a trimer. The reconstitution of MpOmp into black lipid membranes demonstrated its ability to form ion channels whose conductivity depends on the electrolyte concentration. The spatial structure of MpOmp had features typical for the classical gram-negative porins. However, the oligomeric structure of isolated MpOmp was distinguished by very low stability: heat-modified monomer was already observed at 30 ◦C. The data obtained suggest the stabilizing role of lipids in the natural membrane of marine bacteria in the formation of the oligomeric structure of porin.

**Keywords:** marine bacteria; whole genome sequence; porin; amino acids composition; bilayer lipid membrane; pore-forming activity; spatial structure
