Phosphorylation mapping of Laminin β1-chain: Kinases in association with active sites.

Laminins are a major constituent of the extracellular matrix (ECM). Laminin-111, the most extensively studied laminin isoform, consists of the α1, the β1 and the γ1 chain, and is involved in many cellular processes, like adhesion, migration and differentiation. Given the regulatory role of phosphorylation in protein function, it is important to identify the phosphorylation sites of human laminin β1-chain sequence (LAMB1). Therefore, we computationally predicted all possible phosphorylation sites in LAMB1. For the first time, we identified the possibly responsible kinases for already in vitro experimentally observed phosphorylated residues in LAMB1. All known functional (active) sites of LAMB1, were recorded after an extensive literature search and combined with the experimentally observed and our predicted phosphorylated residues. This generated a detailed phosphorylation map of LAMB1. Five kinases (PKA, PKC, CKII, CKI and GPCR1) were indicated important, while the role of PKA, PKC and CKII, kinases known for ectophosphorylation activity, was highlighted. The activity of PKA and PKC was associated with the active site RIQNLLKITNLRIKFVKLHTLGDNLLDS. Also, predicted phosphorylations inside two amyloidogenic (DSITKYFQMSLE, VILQHSAADIAR) and two anti-cancerous (YIGSR and PDSGR) sites suggested a possible role in the development of the corresponding diseases.