Catalyzes the translocation of specific phospholipids from the cytoplasmic to the extracellular/lumenal leaflet of membrane coupled to the hydrolysis of ATP. Thereby, participates in phospholipid transfer to apoliproteins to form nascent high density lipoproteins/HDLs. Transports preferentially phosphatidylcholine over phosphatidylserine. May play a similar role in the efflux of intracellular cholesterol to apoliproteins and the formation of nascent high density lipoproteins/HDLs. ATP + H2O + phospholipidSide 1 = ADP + phosphate + phospholipidSide 2. a 1,2-diacyl-sn-glycero-3-phosphocholine(out) + ATP + H2O = a 1,2-diacyl-sn-glycero-3-phosphocholine(in) + ADP + H(+) + phosphate a 1,2-diacyl-sn-glycero-3-phospho-L-serine(out) + ATP + H2O = a 1,2-diacyl-sn-glycero-3-phospho-L-serine(in) + ADP + H(+) + phosphate a sphingomyelin(in) + ATP + H2O = a sphingomyelin(out) + ADP + H(+) + phosphate ATP + cholesterol(in) + H2O = ADP + cholesterol(out) + H(+) + phosphate ATPase activity is decreased by cholesterol and ceramide. ATPase activity is stimulated by phosphatidylcholine and to a lesser degree by phosphatidylserine and sphingomyelin. Phospholipid translocase activity is highly reduced by berylium fluoride and aluminum flouride and reduced by N-ethylmaleimide. Interacts with MEGF10 (PubMed:17205124). May interact with APOE1; functionally associated with APOE1 in the biogenesis of HDLs (By similarity). Interacts with ABCA8; this interaction potentiates cholesterol efflux (By similarity). Interacts with ABCA12 and NR1H2; this interaction is required for ABCA1 localization to the cell surface and is necessary for its normal activity and stability (By similarity). Widely expressed in adult tissues. Highest levels are found in pregnant uterus and uterus. Down-regulated by endotoxins (LPS) or cytokines (TNF and IL-1) in J774 macrophages. The down-regulation by endotoxin in macrophages is not likely to be mediated by the liver X receptor/retinoic X receptor (LXR/RXR). Multifunctional polypeptide with two homologous halves, each containing a hydrophobic membrane-anchoring domain and an ATP binding cassette (ABC) domain. Phosphorylation on Ser-2054 regulates phospholipid efflux. Palmitoylated by ZDHHC8. Palmitoylation is essential for localization to the plasma membrane. Belongs to the ABC transporter superfamily. ABCA family.