MuLK, a eukaryotic multi-substrate lipid kinase.
We report the identification and characterization of a novel lipid kinase that phosphorylates multiple substrates. This enzyme, which we term MuLK for multi-substrate lipid kinase, does not belong to a previously described lipid kinase family. MuLK has orthologs in many organisms and is broadly expressed in human tissues. Although predicted to be a soluble protein, MuLK co-fractionates with membranes and localizes to an internal membrane compartment. Recombinant MuLK phosphorylates diacylglycerol, ceramide, and 1-acylglycerol but not sphingosine. Although its affinity for diacylglycerol and ceramide are similar, MuLK exhibits a higher V(max) toward diacylglycerol in vitro, consistent with it acting primarily as a diacylglycerol kinase. MuLK activity was inhibited by sphingosine and enhanced by cardiolipin. It was stimulated by calcium when magnesium concentrations were low and inhibited by calcium when magnesium concentrations were high. The effects of charged lipids and cations on MuLK activity in vitro suggest that its activity in vivo is tightly regulated by cellular conditions.
Waggoner
David W
DW
Department of Pharmacology, University of Washington, Seattle, Washington 98195, USA.
Johnson
Laura Beth
LB
Mann
Philip C
PC
Morris
Valerie
V
Guastella
John
J
Bajjalieh
Sandra M
SM
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D002308:Cardiolipins / Q000737:chemistry; D002412:Cations; D002462:Cell Membrane / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D019852:Diacylglycerol Kinase / Q000737:chemistry; D004075:Diglycerides / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D015723:Gene Library; D015894:Genome, Human; D049452:Green Fluorescent Proteins; D006801:Humans; D007477:Ions; D007700:Kinetics; D008055:Lipids / Q000737:chemistry*; D008164:Luminescent Proteins / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010179:Pancreas / Q000378:metabolism; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000235:genetics*; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D013110:Sphingosine / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014018:Tissue Distribution
D002308:Cardiolipins; D002412:Cations; D018076:DNA, Complementary; D004075:Diglycerides; D007477:Ions; D008055:Lipids; D008164:Luminescent Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; C492429:AGK protein, human; D017853:Phosphotransferases (Alcohol Group Acceptor); D019852:Diacylglycerol Kinase; D013110:Sphingosine