Flippases: still more questions than answers

• Published in: Cellular and molecular life sciences : CMLS Vol. 65; no. 20; pp. 3119 - 3125
• Main Authors: Poulsen, L. R, López-Marqués, R. L, Palmgren, M. G
• Format: Journal Article
• Language: English
• Published: Basel Basel : SP Birkhäuser Verlag Basel 01-10-2008; Birkhäuser-Verlag; Springer Nature B.V
• Subjects: Adenosine Triphosphatases - metabolism; Amino Acid Sequence; Animals; Biochemistry; Biomedical and Life Sciences; Biomedicine; Cell Biology; Cellular biology; Enzymes; Eukaryotes; Humans; Life Sciences; Lipid Bilayers - metabolism; Lipids; Membrane Proteins - chemistry; Membrane Proteins - metabolism; Membranes; Molecular Sequence Data; Phospholipid Transfer Proteins - chemistry; Phospholipid Transfer Proteins - metabolism; Phospholipids - metabolism; Protein Transport; Translocation; Visions & Reflections (Minireview); P; Flippases; vesicle formation; phospholipid flipping; ATPases
• ISSN: 1420-682X; 1420-9071
• DOI: 10.1007/s00018-008-8341-6

Our understanding of flippase-mediated lipid translocation and membrane vesiculation, and the involvement of P-type ATPases in these processes is just beginning to emerge. The results obtained so far demonstrate significant complexity within this field and point to major tasks for future research. Most importantly, biochemical characterization of P₄-ATPases is required in order to clarify whether these transporters indeed are capable of catalyzing transmembrane phospholipid flipping. The β-subunit of P₄-ATPases shows unexpected similarities between the β- and γ-subunits of the Na⁺/K⁺-ATPase. It is likely that these proteins provide a similar solution to similar problems, and might have adopted similar structures to accomplish these tasks. No P₄-ATPases have been identified in the endoplasmic reticulum and it remains an intriguing possibility that, in this compartment, P₅A-ATPases are functional homologues of P₄-ATPases.