Abstract

Porins are critical outer membrane proteins in Gram-negative bacteria, facilitating the passive, non-specific diffusion of small, hydrophilic molecules. This study focuses on the comprehensive characterization of a novel porin identified in the psychrophilic marine bacterium *Marinomonas primoryensis*. The primary objective was to elucidate the structural features and functional electrophysiological properties of this newly discovered protein. The purified porin was successfully reconstituted into planar lipid bilayers to analyze its ion channel activity. Electrophysiological measurements revealed that the porin forms stable, voltage-dependent channels with a single-channel conductance of approximately 1.5 nS in 1 M KCl. Furthermore, the channel exhibited a slight cation selectivity and a characteristic barrel-like structure, inferred from its high stability and single-channel behavior. These findings provide fundamental insights into the molecular mechanisms of nutrient uptake and osmotic regulation in *M. primoryensis*, highlighting the unique adaptations of membrane proteins in cold, marine environments. The characterization of this novel porin contributes to the broader understanding of bacterial outer membrane permeability and its role in cellular physiology.