ABSTRACT
Classical genetic methods have been used to investigate protein transport in eukaryote cells. Using this approach, mutant cells deficient in secretion or protein targetting are isolated and the defective genes identified. Yeasts have also been used to investigate membrane protein targetting. In many cases, identification of the gene products in the deficient mutants has shown that these are analogous to proteins identified using biochemical methods in other eukaryotic cells. Protein molecules carry the information which directs them to their final environment. This ‘address tag’ can reside in a specific amino acid sequence or in some part of the structure of the folded protein. Peroxisomal lumenal enzymes, which include a range of oxidative enzymes, are synthesized in the cytosol and targetted to the peroxisome post-translationally. The targetting sequence for peroxisomal enzymes was identified by comparison of the amino acid sequences of the peroxisomal enzyme which had been deposited in data bases.
