Q.26 Which types of protein is commonly found in RBC?

1. Glyoprotein
2. Spectrin
3. Ankyrin
4. Spectrin and Ankyrin

Spectrin and ankyrin are key cytoskeletal proteins commonly found in red blood cells (RBCs), working together to maintain membrane structure and flexibility. The correct answer is option 4: Spectrin and Ankyrin.

Question Overview

The query identifies proteins typically abundant in RBC membranes: 1. Glycoprotein, 2. Spectrin, 3. Ankyrin, 4. Spectrin and Ankyrin. RBCs rely on a spectrin-based cytoskeleton for biconcave shape, deformability during circulation, and resistance to shear stress.

Correct Answer: Option 4

Spectrin forms a flexible meshwork lining the inner membrane, while ankyrin anchors it to band 3 (anion exchanger). Both are hallmark RBC proteins; mutations cause hereditary spherocytosis. They interact directly—ankyrin’s repeats bind spectrin’s β-chain.

Glycoprotein Analysis

Glycoproteins like glycophorin A and band 3 occur on RBC surfaces for antigenicity and transport but are integral membrane proteins, not the primary cytoskeletal types. They contribute ~1-2% to membrane mass, unlike abundant spectrin (25-30%).

Spectrin Details

α/β-Spectrin heterodimers self-associate into tetramers, forming a hexagonal lattice with actin junctions. Essential for elasticity; defects lead to fragile, spherical RBCs. RBC spectrin (αI variant) is mammal-specific for enucleated cells.

Ankyrin Details

Ankyrin-R (band 2.1) links spectrin to band 3 and protein 4.2, forming vertical membrane connections. Its repeats (24 total) bind multiple partners; central domain grips spectrin. Critical for skeleton-membrane tethering.

Exam Tips

Memorize RBC skeleton core: spectrin-actin-4.1 (horizontal), ankyrin-band 3-4.2 (vertical). Glycoproteins are “membrane-spanning,” not “cytoskeletal.” Visualize: spectrin as rods, ankyrin as hooks.