Membrane-snorkeling basic residues in transmembrane domains.

(A) Percentage distribution of single-span transmembrane proteins containing intramembrane Lys or Arg, both Lys and Arg, or no Lys or Arg. Data sets include single-span transmembrane proteins from yeast (Saccharomyces cerevisiae), human (Homo sapiens), as well as human single-span transmembrane proteins located at the PM (of H. sapiens) [28]. (B) Location of intramembrane basic residue. The x-axis indicates the distance of intramembrane basic residue from the TMD/CD border, and “1” means the first TMD residue on the border. Supporting data are compiled in S1 Data. The underlying data of panel A and B can be found in http://dx.doi.org/10.17632/tg2622h9dd.1. (C) Sequence alignment of eight human integrin β subunit TMDs. The conserved intramembrane Lys/Arg are highlighted in red. Residues are numbered according to the human β2 sequence. Lys, lysine; Arg, arginine; CD, cytoplasmic domain; TMD, transmembrane domain; PM, plasma membrane.