Amino acids in a membrane protein

Membrane proteins are a class of proteins that are embedded within or associated with the cell membrane. They play crucial roles in various cellular processes, including cell signaling, transport of molecules across the membrane, and cell adhesion. The structure and function of membrane proteins are determined by the arrangement of their amino acids.

The hydrophobic core of the membrane protein

The structure of a membrane protein consists of both hydrophilic and hydrophobic regions. The hydrophobic regions, which are composed of nonpolar amino acids, are typically buried within the interior of the protein structure, shielded from the surrounding aqueous environment. These hydrophobic amino acids help anchor the protein in the lipid bilayer of the cell membrane.

Buried amino acids

The amino acids that are most likely to be buried in the interior of the protein structure are those with hydrophobic side chains. These include amino acids such as alanine, leucine, isoleucine, valine, phenylalanine, tryptophan, and methionine. These hydrophobic amino acids have nonpolar side chains, which allows them to interact favorably with the hydrophobic core of the protein.

Hydrophilic amino acids

On the other hand, hydrophilic amino acids, which have polar or charged side chains, are more likely to be located on the surface of the membrane protein, exposed to the aqueous environment. These amino acids can form hydrogen bonds with water molecules or interact with other polar or charged residues on the protein surface.

Aspartic acid and glutamic acid

Aspartic acid and glutamic acid are both hydrophilic amino acids with negatively charged side chains. They are classified as acidic amino acids due to their ability to donate protons. These amino acids are not likely to be buried in the interior of the protein structure because their charged side chains would repel the hydrophobic environment. Instead, they are often found on the surface of the membrane protein, where they can interact with water molecules or participate in electrostatic interactions with other charged residues.

Methionine and tyrosine

Methionine and tyrosine are both hydrophobic amino acids that have nonpolar side chains. Methionine is an essential amino acid with a sulfur-containing side chain, while tyrosine is a nonessential amino acid with an aromatic side chain. These amino acids are more likely to be buried in the interior of the protein structure, away from the aqueous environment, due to their hydrophobic nature.

Therefore, the correct answer is options A, B, and C. Aspartic acid, glutamic acid, methionine, and tyrosine are all amino acids that are not most likely to be buried in the interior of a membrane protein structure.