21. Which protein structure is most consistent for the hydropathy graph of the intrinsic membraneprotein shown below?+168 F+84-84-16820100200300First amino acid in windowA) A seven-helix serpentine receptorB) A Type I integral membrane proteinC) A Type Il integral membrane proteinD) A GPI-anchored proteinE) A beta-barrel protein with about 10 membrane-spanning strands.Hydropathy index (kJ mol-1)

Hydropathy graph depicts the hydrophobicity and hydrophilicity of a polypeptide chain based on the amino acid sequence. this we can obtain from online tools by input of amino acid sequence of any polypeptide/peptide. This gives us the information about the protein like it is hydrophobic completely (inside the cell membrane like pore proteins), hydrophilic completely (it must be interacting with other protein or ligand, extracellularly or intracellularly) and mix hydrophobic- hydrophilic (both cell membrane integral domain and extra/intracellular interacting domain present). Protein structure is a three dimensional structure of a polypeptide chain. Integral membrane proteins (IMP) are class of protein which is permanently attached to the biological cell membrane and transmembrane proteins (TM) are IMP. But, all IMP are not transmembrane protein. IMP can have membrane which spans in both side (extracellularly/intracellularly) and one side either. mostly function as a transporter, enzymes, receptor, structural;, cell adhesion etc. Cell membrane separates the intracellular part from extracellular part which is compose of protein and lipids. Domains of proteins can be hydrophobic and hydrophilic as per the need of the cell function. A) Seven helix serpentine receptors belongs to large class of protein called as seven transmembrane receptor (also known as G-protein coupled receptor). It have three component extracellular part (receives the signal via ligand/hormones), transmembrane and intracellular (transmits the signal). Thus, the given hydropathy graph is appropriate for "Seven helix serpentine receptors" kind of protein sequence. B) Type I integral membrane protein belongs to the class of transmembrane protein which is permanently bound to biological cell membrane and positioned in such way that their carboxyl termini is towards the cytosol. This can have polypeptide chain hanging in both cytosol and extracellular region. Thus, the given hydropathy graph is appropriate for "Type I integral membrane protein" kind of protein sequence. C) Type II integral membrane protein belongs to the class of transmembrane protein which is permanently bound to biological cell membrane and positioned in such way that their amino termini is towards the cytosol. This can have polypeptide chain hanging in both cytosol and extracellular region. Thus, the given hydropathy graph is appropriate for "Type II integral membrane protein" kind of protein sequence. D) GPI anchored protein belongs to a type I integral membrane protein and GPI anchored protein involve in membrane transport protein, cell adhesion, protection of surface and synthesis of cell wall. It is a very small microdomains membrane protein which is densely glycosylated. It is just attached to the cell membrane and completely present toward to extracellular side (luminal) of the cell membrane. Thus, the given hydropathy graph is NOT appropriate for "GPI anchored protein" kind of protein sequence. E) A beta barrel protein is a membrane protein which is composed of tandem repeats of beta-sheet. It twists and coils to form a closed toroidal like structure. example of beta barrels protein is Porin which have hydrophobic residues oriented toward the exterior polypeptide chain i.e. towards lipids, and hydrophilic residues oriented toward the aqueous interior pore side as it is use in the transport of biomolecules. So in the given hydropathy graph N-termini and C-termini have hydrophilic residues and middle part of protein is consist of hydrophobic residues. Thus, the given hydropathy graph is NOT appropriate for "A beta barrel protein" kind of protein sequence.Hence, the given hydropathy graph is most consistent with Seven helix serpentine receptors, Type I integral membrane protein, and Type II integral membrane protein sequence.