Membrane Proteins|: cytoskeleton and membrane protein syntheis Flashcards
Haemolytic anaemias
Heriditary Spherocytosis
- spectrin depleted by 40-50%
- less resistant to lysis
- cleared by spleen
- erythrocytes round up
Heriditary Ellptocytosis
- Defect in spectrin molecule
- unable to form heteroterotramers
- fragile elliptoid cells
Secreted Protein biosynthesis
synthesised differently
1. arrested so it can be transferred to the membranes to be passed across the membrane into a vesicle
- Amino acids on the end terminus are recognised by a large ribonuclear particle called Signal recognition particle- SRP
- the SRP binds to the secreted protein and the ribosome and prevents further synthesis
- the SRP is recognised by a docking protein in the ER
Erythrocytes cytoskeleton
Spectra and actin are anchored to the erythrocytes membrane via adapter proteins called ankyrin and bad 4.1 to integral membrane proteins called band 3 and glycophorin A
How are cytosolic and membrane proteins directed to the ER membrane and what enables the insertion of the membrane protein
Cytosolic and membrane proteins are synthesised by ribosomes.
When the SRP recognises the leading sequence at the N terminal end, it halts protein synthesis on the ribosome. The SRP recognised by the signal sequence receptor on the ER membrane, which is part of the protein translocator complex.
The protein synthesis is sent through the pore of this translocator.
Membrane proteins have a hydrophobic sequence known as the stop transfer signal, which stops the movement of the membrane protein. Thereby embedding the newly synthesised protein into the ER membrane.
Describe the structure of the cytoskeleton of red blood cells?
band 3: anchor the cytoskeleton Ankyrin (band 4.9): bind cytoskeleton to membrane protein
Band 4.1: regulate ankyrins affinity to band 3
alpha and beta spectrin: gives RBCs their shape and interacts with actin filaments in the cytoplasm
actin binds to spectrin binds to ankyrin binds to band 3
