Degrades abnormal exported proteins and responsible for the propeptide processing of a natural pro-protein and for the maturation of a native protein. It also plays a prominent role in stress (heat shock, ethanol, puromycin and NaCl) resistance during active exponential growth (Probable). Acts on substrates that are at least partially unfolded. The cleavage site P1 residue is normally between a pair of hydrophobic residues, such as Val-|-Val. Transcription is CssS dependent. Induced by heat shock during exponential growth and by heterologous amylases at the transition phase of the growth cycle. Negatively regulates its own expression during exponential growth and during heat shock. In contrast to other bacteria, in which inactivation of serine protease leads to thermosensitivity, inactivation of HtrA leads to an increased thermotolerance and an increased tolerance to hydrogen peroxide. Inactivation of both HtrA and HtrB leads to growth defects and to thermosensitivity. Inactivation results in compensating overexpression of YtvA, especially during stress conditions. Belongs to the peptidase S1C family.