Chemo-enzymatic synthesis of NPN cofactor taking advantage of ADP-ribosyl cyclase and LarC cyclometallase promiscuous activities.

The nickel-pincer nucleotide cofactor (NPN) is a widespread organometallic cofactor required for lactate racemase (LarA) and for α-hydroxy acid racemases and epimerases of the LarA superfamily. Its biosynthesis, which starts with nicotinic acid adenine dinucleotide (NaAD), requires three enzymes: LarB, LarC, and LarE, and can be performed in vitro with purified enzymes. Nevertheless, as LarE and LarC are single turnover enzymes, the in vitro NPN biosynthesis requires huge amounts of enzymes (particularly 2 equivalents of LarE), which hampers the study of NPN and of NPN-dependent enzymes.

PBP-A, a cyanobacterial DD-peptidase with high specificity for amidated muropeptides, exhibits pH-dependent promiscuous activity harmful to Escherichia coli.

Penicillin binding proteins (PBPs) are involved in biosynthesis, remodeling and recycling of peptidoglycan (PG) in bacteria. PBP-A from Thermosynechococcus elongatus belongs to a cyanobacterial family of enzymes sharing close structural and phylogenetic proximity to class A β-lactamases. With the long-term aim of converting PBP-A into a β-lactamase by directed evolution, we simulated what may happen when an organism like Escherichia coli acquires such a new PBP and observed growth defect associated with the enzyme activity.

Competence shut-off by intracellular pheromone degradation in salivarius streptococci.

Competence for DNA transformation is a major strategy for bacterial adaptation and survival. Yet, this successful tactic is energy-consuming, shifts dramatically the metabolism, and transitory impairs the regular cell-cycle. In streptococci, complex regulatory pathways control competence deactivation to narrow its development to a sharp window of time, a process known as competence shut-off.

Coevolution of the bacterial pheromone ComS and sensor ComR fine-tunes natural transformation in streptococci.

Competence for natural transformation extensively contributes to genome evolution and the rapid adaptability of bacteria dwelling in challenging environments. In most streptococci, this process is tightly controlled by the ComRS signaling system, which is activated through the direct interaction between the (R)RNPP-type ComR sensor and XIP pheromone (mature ComS). The overall mechanism of activation and the basis of pheromone selectivity have been previously reported in Gram-positive salivarius streptococci; however, detailed 3D-remodeling of ComR leading up to its activation remains only partially understood.