MlaC belongs to a unique class of non-canonical substrate-binding proteins and follows a novel phospholipid-binding mechanism.

The outer membrane (OM) of Gram-negative bacteria acts as a formidable barrier against a plethora of detrimental compounds owing to its asymmetric nature. This is because the OM possesses lipopolysaccharides (LPSs) in the outer leaflet and phospholipids (PLs) in the inner leaflet. The maintenance of lipid asymmetry (Mla) system is involved in preserving the distribution of PLs in OM. The periplasmic component of the system MlaC serves as the substrate-binding protein (SBP) that shuttles PLs between the inner and outer membranes. However, an in-depth report highlighting its mechanism of ligand binding is still lacking. This study reports the crystal structure of MlaC from Escherichia coli (EcMlaC) at a resolution of 2.5 Å in a quasi-open state, complexed with PL. The structural analysis reveals that EcMlaC and orthologs comprise two major domains, viz. nuclear transport factor 2-like (NTF2-like) and phospholipid-binding protein (PBP). Each domain can be further divided into two subdomains arranged in a discontinuous fashion. This study further reveals that EcMlaC is polyspecific in nature and follows a reverse mechanism of the opening of the substrate-binding site during the ligand binding. Furthermore, MlaC can bind two PLs by forming subsites in the binding pocket. These findings, altogether, have led to the proposition of the unique "segmented domain movement" mechanism of PL binding, not reported for any known SBP to date. Further, unlike typical SBPs, MlaC has originated from a cystatin-like fold. Overall, this study establishes MlaC to be a non-canonical SBP with a unique ligand-binding mechanism.

Design of novel PhMTNA inhibitors, targeting neurological disorder through homology modeling, molecular docking, and dynamics approaches.

Vanishing white matter (VWM) is a hereditary human disease, mostly prevalent in childhood caused by the defects in the eukaryotic initiation factor beta subunits. It is the first disease involved in the translation initiation factor, eIF2B. There is no specific treatment for VWM which mainly affect the brain and ovaries. The gray matter remains normal in all characteristics while the white matter changes texture, coming to the pathophysiology, many initiation factors are involved in the initiation of translation of mRNAs into polypeptides. In this study, the three-dimensional structure of PhMTNA protein was modeled and the stability ascertained through Molecular dynamic simulation (MDS) for 100 ns. The active site residues are conserved with the reported BsMTNA structure which is also confirmed through sitemap prediction. Through virtual screening and induced fit docking, top five leads against PhMTNA protein was identified based on their binding mode and affinity. ADME properties and DFT (Density Functional Theory) studies of these compounds were studied. In addition to that, computational mutagenesis studies were performed to identify the hotspot residues involved in the protein-ligand interactions. Overall analysis showed that the compound NCI_941 has a highest binding energy of -46.256 kcal mol-1 in the Arg57Ala mutant. Thus, the results suggest that NCI_941 would act as a potent inhibitor against PhMTNA protein.