Which amino acids would most likely reside in the membrane-spanning domain of a membrane-embedded protein?

The amino acids that would most likely reside  in the membrane spanning domain of a membrane embedded protein are LEUCINE, THERONINE AND LYSINE. This is because, these amino acids have hydrophobic side chains and one or more membrane spanning domains.
Membrane protein are usually made up of amino acids which have hydrophobic side chains that interact with the fatty acyl group of the membrane phospholipids, thereby anchoring the protein to the membrane.