GENETIC-STUDIES REVEAL THAT MYRISTOYLCOA-PROTEIN N-MYRISTOYLTRANSFERASE IS AN ESSENTIAL ENZYME IN CANDIDA-ALBICANS

MyristoylCoA:protein N-myristoyltransferase (Nmt) catalyses the co-tra nslational, covalent attachment of myristate (C14:0) to the amino-term inal glycine residue of a number of eukaryotic proteins involved in ce llular growth and signal transduction. The NMT1 gene is essential for vegetative growth of Saccharomyces cerevisiae, Studies were carried ou t to determine if Nmt is also essential for vegetative growth of the p athogenic fungus Candida albicans. A strain of C. albicans was constru cted in which one copy of NMT was partially deleted and disrupted. A G ly-447 --> Asp mutation was introduced into the second NMT allele. Thi s mutation produced marked reductions in catalytic efficiency at 24 an d 37 degrees C, as judged by in vitro kinetic studies of the wild-type and mutant enzymes which had been expressed in, and purified from, Es cherichia coil, The growth characteristics of isogenic NMT/NMT, NMT/De lta nmt, and nmt Delta/nmtG447D C. albicans strains were assessed unde r a variety of conditions. Only the nmt Delta/nmtG447D strain required myristate for growth. This was true at both 24 and 37 degrees C, Palm itate could not substitute for myristate, Incubation of nmt Delta/nmtG 447D cells at 37 degrees C in the absence of myristate resulted in cel l death as observed by the inability to form colonies on media supplem ented with 500 mu M myristate, Studies in an immunosuppressed-mouse mo del of C. albicans infection revealed that the NMT/Delta nmt strain pr oduced 100% lethality within 7d after intravenous administration while the isogenic nmt Delta/nmtG447G strain produced no deaths even after 21 d. These observations establish that Nmt is essential for vegetativ e growth of C. albicans and suggest that inhibitors of this acyltransf erase may be therapeutically useful fungicidal agents.