KCNMB2 and chronic obstructive pulmonary disease: Smoking and COPD phenotype interacting gene, KCNMB2 (potassium large-conductance calcium-activated channel, subfamily M, beta member 2), a potassium channel gene, it encodes the β-subunits of the large-conductance K+ channels, which is important for the control of smooth muscle tone and neuronal excitability.