The 67-kDa laminin receptor originated from a ribosomal protein that acquired a dual function during evolution

The 67-kDa laminin receptor (67LR) is a nonintegrin cell surface receptorthat mediates high-affinity interactions between cells and laminin.Overexpression of this protein in tumor cells has been related to tumorinvasion and metastasis. Thus far, only a full-length gene encoding a37-kDa precursor protein (37LRP) has been isolated. The finding that thecDNA for the 37LRP is virtually identical to a cDNA encoding the ribosomalprotein p40 has suggested that 37LRP is actually a component of thetranslational machinery, with no laminin-binding activity. On the otherhand, a peptide of 20 amino acids deduced from the sequence of 37LR/p40 wasshown to exhibit high laminin-binding activity. The evolutionaryrelationship between 23 sequences of 37LRP/p40 proteins was analyzed. Thisphylogenetic analysis indicated that all of the protein sequences derivefrom orthologous genes and that the 37LRP is indeed a ribosomal proteinthat acquired the novel function of laminin receptor during evolution. Theevolutionary analysis of the sequence identified as the laminin-bindingsite in the human protein suggested that the acquisition of thelaminin-binding capability is linked to the palindromic sequence LMWWML,which appeared during evolution concomitantly with laminin.