LACTB is a filament-forming protein localized in mitochondria.

LACTB is a mammalian active-site serine protein that has evolved from a bacterial penicillin-binding protein. Penicillin-binding proteins are involved in the metabolism of peptidoglycan, the major bacterial cell wall constituent, implying that LACTB has been endowed with novel biochemical properties during eukaryote evolution. Here we demonstrate that LACTB is localized in the mitochondrial intermembrane space, where it is polymerized into stable filaments with a length extending more than a hundred nanometers.

Evolution of a family of metazoan active-site-serine enzymes from penicillin-binding proteins: a novel facet of the bacterial legacy.

Background: Bacterial penicillin-binding proteins and beta-lactamases (PBP-betaLs) constitute a large family of serine proteases that perform essential functions in the synthesis and maintenance of peptidoglycan. Intriguingly, genes encoding PBP-betaL homologs occur in many metazoan genomes including humans. The emerging role of LACTB, a mammalian mitochondrial PBP-betaL homolog, in metabolic signaling prompted us to investigate the evolutionary history of metazoan PBP-betaL proteins.

Expression and purification of the mitochondrial serine protease LACTB as an N-terminal GST fusion protein in Escherichia coli.

LACTB is a mammalian mitochondrial protein sharing sequence similarity to the beta-lactamase/penicillin-binding protein family of serine proteases that are involved in bacterial cell wall metabolism. The physiological role of LACTB is unclear. In this study we have subcloned the cDNA of mouse LACTB (mLACTB) and produced recombinant mLACTB protein in Escherichia coli.