In B. subtilis, one small SOS response operon under the control of LexA, the yneA operon, is comprised of three genes: yneA, yneB, and ynzC. This family consists of several short, hypothetical bacterial proteins of unknown function. These proteins are mainly found in gram-positive firmicutes. Structures show that the N-terminus is composed of two alpha helices forming a helix-loop-helix motif. The structure of ynzC from B. subtilis forms a trimeric complex. Structural modelling suggests this domain may bind nucleic acids. This family is also known as UPF0291.