Tetratricopeptide repeat domain of Yarrowia lipolytica Pex5p is essential for recognition of the type 1 peroxisomal targeting signal but does not confer full biological activity on Pex5p

Peroxins are proteins required for peroxisome assembly and are encoded by t he PEX genes. The Yarrowia lipolytica pex5-1 mutant fails to import a subse t of peroxisomal matrix proteins, including those with a type 1 peroxisomal targeting signal(PTS1). Pex5p family members interact with a PTSI through their characteristic tetratricopeptide repeat (TPR) domain. We used binding assays in vitro to investigate the nature of the association of Y. lipolyt ica Pex5p (YlPex5p) with the PTS1 signal. A purified recombinant YlPex5p fu sion protein interacted specifically, directly and autonomously with a prot ein terminating in a PTS1. Wild-type YlPex5p translated in vitro recognized functional PTS1s specifically. This activity is abrogated by the substitut ion of an aspartic residue for a conserved glycine residue in the TPR domai n (G455D) of YlPex5p encoded by the pex5-1 allele. Deletion analysis demons trated that an intact TPR domain of YlPex5p is necessary but not sufficient for both interaction with a PTS1 and functional complementation of a strai n lacking YlPex5p.