Exploring the interactions between Vinculin and vinculin-binding site containing proteins

Focal adhesion complexes are mechanosensitive adhesion complexes that regulate keycellular processes such as cell migration and cell survival. These complexes connectthe extracellular matrix (ECM) to the Actin network through a matrix-Integrin-TalinVinculin-Actin complex. Vinculin is a linker protein that through its N-terminal headdomain (VD1) binds to cryptic vinculin binding sites (VBS) in talin, while its tail domainbinds to actin linking the actin network to the ECM. This study investigates keyinteractions between vinculin and VBS containing proteins. Proteins such as thechlamydial virulence factor TarP which hijacks vinculin to aid in bacterial internalisation,the Talin helix 50 VBS which seems unique in its ability to accommodate VD1 mutationsthat disrupt binding and lastly α-Catulin a vinculin homologue which could shareinteractions with any known vinculin binding proteins.We identified that the C.caviae Tarp VBS3 showed increased affinity for VD1 comparedto the VBS1 and Pulldown assays showed that TarP may bind VD1 in a 1:3 ratio. Wepropose that TarP binding VD1 in a 1:3 ratio alongside the differences in affinitybetween its VBS indicate the possibility of infection stage specificity between VBSs.Talin H50 appears to accommodate VD1 mutants due to of lack polar/ionic bonds,alongside smaller side chained amino acids in the interface when compared to otherVBS.Lastly, α-catulin shows conserved secondary structure with vinculin, as well as apotential interaction between α-catulin and the adhesion protein Paxillin. Indicating thatα-catulin like vinculin may bind paxillin and be recruited to focal adhesion complexes.