TerC proteins function during protein secretion to metalate exoenzymes

Cytosolic metalloenzymes acquire metals from buffered intracellular pools. How exported metalloenzymes are appropriately metalated is less clear. We provide evidence that TerC family proteins function in metalation of enzymes during export through the general secretion (Sec-dependent) pathway. Bacillus subtilis strains lacking MeeF(YceF) and MeeY(YkoY) have a reduced capacity for protein export and a greatly reduced level of manganese (Mn) in the secreted proteome. MeeF and MeeY copurify with proteins of the general secretory pathway, and in their absence the FtsH membrane protease is essential for viability. MeeF and MeeY are also required for efficient function of the Mn2+-dependent lipoteichoic acid synthase (LtaS), a membrane-localized enzyme with an extracytoplasmic active site. Thus, MeeF and MeeY, representative of the widely conserved TerC family of membrane transporters, function in the co-translocational metalation of Mn2+-dependent membrane and extracellular enzymes. TerC family membrane proteins associate with the general protein secretion complex to facilitate the co-translocational loading of Mn(II) into nascent metalloenzymes. Here, the authors show that Bacillus subtilis mutants lacking TerC proteins are defective in production of the membrane-embedded lipoteichoic acid synthase and secreted proteases.

Automated summary

In this study, the authors provide evidence that TerC family proteins are involved in the metalation of enzymes during export through the general secretion pathway. They found that Bacillus subtilis strains lacking MeeF and MeeY have reduced protein export capacity and decreased levels of manganese in the secreted proteome. MeeF and MeeY co-purify with proteins of the general secretory pathway and are essential for the function of the Mn2+-dependent lipoteichoic acid synthase.