PEROXISOMAL AMINE OXIDASE OF HANSENULA-POLYMORPHA DOES NOT REQUIRE ITS SRL-CONTAINING C-TERMINAL SEQUENCE FOR TARGETING

Amine oxidase (AMO) is a peroxisomal matrix protein of Hansenula polym orpha, which is induced during growth of the yeast in media containing primary amines as a sole nitrogen source. The deduced amino acid sequ ence of the protein contains an SRL sequence at nine amino acids from the C-terminus. In this study, we have examined the possible role of t he SRL motif in sorting of AMO to peroxisomes by mutating the correspo nding gene sequence. For this purpose, we have developed a DNA constru ct that is specifically integrated into the AMO locus of the H. polymo rpha genome, placing the mutant gene under the control of the endogeno us AMO promoter and eliminating expression of the wild-type gene. Anal ysis of a stable transformant, containing the desired gene configurati on, showed that mutation of the C-terminal sequence neither interfered with correct targeting of the protein into the peroxisome nor display ed significant effects on its activity. From this, it was concluded th at the SRL-containing C-terminus is not essential for peroxisomal targ eting of AMO in H. polymorpha.