Twists and turns

The Cytoplasmic Loop between Putative Transmembrane Segments 6 and 7 in Sarcoplasmic Reticulum Ca2+-ATPase Binds Ca2+ and Is Functionally Important

“…Thus the detailed organization of cytoplasmic regions and transmembrane segments in domains with defined functional properties still remains a matter of speculation. Based on amino acid similarities, it is reasonable to postulate that, within each group, the topology and the fundamental reaction mechanism exhibit common features (6,15).…”