We originally identified StarD10 as a protein overexpressed in breast cancer 
that cooperates with the ErbB family of receptor tyrosine kinases in cellular 
transformation. StarD10 contains a steroidogenic acute regulatory protein 
(StAR/StarD1)-related lipid transfer (START) domain that is thought to mediate 
binding of lipids. We now provide evidence that StarD10 interacts with 
phosphatidylcholine (PC) and phosphatidylethanolamine (PE) by electron spin 
resonance measurement. Interaction with these phospholipids was verified in a 
fluorescence resonance energy transfer-based assay with 
7-nitro-2,1,3-benzoxadiazol-4-yl-labeled lipids. Binding was not restricted to 
lipid analogs since StarD10 selectively extracted PC and PE from small 
unilamellar vesicles prepared with endogenous radiolabeled lipids from Vero 
monkey kidney cells. Mass spectrometry revealed that StarD10 preferentially 
selects lipid species containing a palmitoyl or stearoyl chain on the sn-1 and 
an unsaturated fatty acyl chain (18:1 or 18:2) on the sn-2 position. StarD10 was 
further shown to bind lipids in vivo by cross-linking of protein expressed in 
transfected HEK-293T cells with photoactivable phosphatidylcholine. In addition 
to a lipid binding function, StarD10 transferred PC and PE between membranes. 
Interestingly, these lipid binding and transfer specificities distinguish 
StarD10 from the related START domain proteins Pctp and CERT, suggesting a 
distinct biological function.