Final answer:
The C-terminal sequence KKKKKXXC likely attaches to the membrane through the lipidation of the cysteine residue. This lipid anchor differs from other membrane protein interactions, such as spanning the membrane or interaction with other membrane proteins.
Step-by-step explanation:
The most likely way in which the C-terminal sequence attaches these proteins to the membrane is likely through the involvement of the cysteine residue at the end of the sequence. This sequence indicates a post-translational modification where the cysteine residue is covalently linked to a lipid molecule in the membrane, a process known as lipidation. The sequence KKKKKXXC suggests that the lipidation occurs through the cysteine at the end (denoted by 'C'), which becomes covalently attached to a fatty acid chain, likely a prenyl group or a fatty acyl group. This type of anchor is categorized as a lipid anchor, which differs from transmembrane proteins that span the membrane with hydrophobic alpha-helices.
It is important to note that the other options are less likely. The peptide spanning the membrane as an alpha helix or beta sheet would require a stretch of hydrophobic amino acids to interact with the hydrophobic core of the membrane lipid bilayer, which is not indicated by the sequence provided. Similarly, the positively charged lysine residues (denoted by 'K') engaging with an acidic integral membrane protein is an unlikely primary mechanism for membrane attachment because the sequence given is a signal for covalent lipid attachment.