Abstract

The paxillin LD motif was first found in the sequence of the protein paxillin and is named after a conserved Leu-Pro residue pair. Paxillin and its paralogues Leupaxin and TGFB1i1 are adaptor proteins that localize to the cytosolic side of focal adhesion complexes. Paxillin is a protein involved in integrin-mediated signalling for cell adhesion, motility and growth-factor inputs. It possesses five copies of the LD motif, short peptide sequences that bind as alpha-helices to the FAT domain of FAK and PYK2 kinases. Some of these repeat motifs also bind to FAT-like domains in Vinculin and GIT1 as well as to proteins with clearly different folds including the CH domain of alpha-parvin. Thus LD motifs appear to be part of complex multiway switching systems affecting cell state via the adhesion complexes. They can be targets for viral interference as has been reported for the BPV E6 protein.



The LD motif entry in ELM is based on the FAK and PYK2 FAT domain interactions. As more data accumulates, it may be desirable to define overlapping motifs for the other helical interactions made by the LD regions of the paxillin family proteins.