The yeast casein kinase Yck3p is palmitoylated, then sorted to the vacuolar membrane with AP-3-dependent recognition of a YXXPhi adaptin sorting signal.
Our previous work found the two yeast plasma membrane-localized casein kinases Yck1p and Yck2p to be palmitoylated on C-terminal Cys-Cys sequences by the palmitoyl transferase Akr1p. The present work examines a third casein kinase, Yck3p, which ends with the C-terminal sequence Cys-Cys-Cys-Cys-Phe-Cys-Cys-Cys. Yck3p is palmitoylated and localized to the vacuolar membrane. While the C-terminal cysteines are required for this palmitoylation, Akr1p is not. Palmitoylation requires the C-terminal Yck3p residues 463-524, whereas information for vacuolar sorting maps to the 409-462 interval. Vacuolar sorting is disrupted in cis through deletion of the 409-462 sequences and in trans through mutation of the AP-3 adaptin complex; both cis- and trans-mutations result in Yck3p missorting to the plasma membrane. This missorted Yck3p restores 37 degrees C viability to yck1Delta yck2-ts cells. yck1Delta yck2-ts suppressor mutations isolated within the YCK3 gene identify the Yck3p vacuolar sorting signal-the tetrapeptide YDSI, a perfect fit to the YXXPhi adaptin-binding consensus. Although YXXPhi signals have a well-appreciated role in the adaptin-mediated sorting of mammalian cells, this is the first signal of this class to be identified in yeast.
Sun
Beimeng
B
Department of Pharmacology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Chen
Linyi
L
Cao
Wei
W
Roth
Amy F
AF
Davis
Nicholas G
NG
D000217:Acyltransferases; D047389:Casein Kinase I; D047388:Casein Kinases; D003545:Cysteine / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D011494:Protein Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*
D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D000217:Acyltransferases; C107846:AKR1 protein, S cerevisiae; D011494:Protein Kinases; D047389:Casein Kinase I; D047388:Casein Kinases; C479666:YCK2 protein, S cerevisiae; D003545:Cysteine