Toxic component of a type I toxin-antitoxin (TA) system. May be a toxic protein; overexpression causes cessation of growth and rapid membrane depolarization. Overexpression induces stress-response and a number of membrane protein genes. In exponential phase. The ohsC RNA (previously known as ryfC) prevents the toxic effects of shoB overproduction, probably by repressing its translation. Expression of the proteinaceous toxin is controlled by antisense sRNA OhsC. Entirely encoded within a small RNA previously known as ryfB.