Localization and targeting of the Saccharomyces cerevisiae Kre2p/Mnt1p alpha 1,2-mannosyltransferase to a medial-Golgi compartment

Kre2,~ 31% Figure 9 . Activity of chimeric proteins. Enzymatic activity was measured in vitro by ed,2-mannosyltransferase assays of membrane preparations, and in vivo mannosylation of cell-wall proteins was assessed by verifying K1 killer toxin sensitivity in a wild-type strain and a kre2 null mutant containing KRE2 and chimeric constructs expressed from the centromeric-based plasmid pRS316 (Sikorski and Hieter, 1989) . Enzymatic activity is expressed as percentages of specific activity (mmot/h/mg) for each chimeric protein. A kre2 null strain expressing KRE2 from pRS316 arbitrarily represents 100% specific activity. Concentrated K1 killer toxin was spotted on a lawn of ~,106/ml cells from a fresh culture of each strain (see Materials and Methods).