21. Which of the following proteins would elute last from a size exclusion colum
ID: 202532 • Letter: 2
Question
21. Which of the following proteins would elute last from a size exclusion column assuming they have been successfully isolated from the plasma membrane and are solubilized in buffer? A) AQP1 (each monomer has a Mr of 28,000) B) K* Channel (41 kD) C) GLUT1 (Mr~45,000) D) GLUT2 (approx. 400 amino acid residues) E) Lactose permease (417 amino acid residues) 22. Examine the hydropathy plot and answer the following question 74 93 The glycophorin protein is primarily an helix that: Series "Exclosure Plots" Point "Middle" Value: 1784 A) is a peripheral membrane protein B) traverses the membrane three times from residues 1 to 20, 25 to 45, and 100 to 120 C) traverses the membrane once from residues 74-93 D) has a cytoplasmic N terminus and a cytoplasmic C terminus E) C and D are correct 100 Amino acid residue # 50 N-terminus C-terminusExplanation / Answer
21. Size exclusion chromatography separates proteins on basis of molecular weight. The material filled in the column results in pores. Larger sized particles will not be stuck in the pores and hence will be eluted out first. The smaller sized particles are trapped in the pores and will be eluted last. Proteins of larger molecular weight will therefore be eluted first as they do not enter pores of the column. The proteins with smaller molecular weight will elute last as they will be trapped in the pores.
On an average 110 Da is 1 amino acid. Hence, 400 amino acids in GLUT2 will be 400*110= 4400.0 Da. 1000Da is 1kDa or 1 kD. Hence, GLUT2 has a molecular weight of 44 kD.
AQPI monomer will have a molecular weight of 28000/1000= 28kD. Each AQPI will exist as tetramer in cell membrane. Hence its size will be 28*4=112 kD.
Lactose Permease will have a molecular weight of 417*110/1000= 45.87 kD.
K+ channel has molecular weight of 41 kD.
Right choice is B. K+ channels.
22. Hydropathy plots allow visualization of hydrophobicity along a peptide sequence. A protein with a transmembrane domain will have hydrophobic amino acids.
Glycophorin is a transmembrane proteins with a cytoplasmic C-terminus and a extracellular N terminus. The amino acids 74-93 form a peak in the hydropathy plot. This indicates that these amino acids are hydrophobic and therefore will be present embedded in the plasma membrane, as the amino acids repel water. The other amino acids are not hydrophobic. Hence, there is a single transmembrane domain corresponding to amino acids 74-93.
Right option is C. traverses the membrane once from residues 74-93.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.