3. A mutation that causes a substitution from leucine to another amino acid alte

Question

3. A mutation that causes a substitution from leucine to another amino acid alters the mobility of a protein in native gel electrophoresis at neutral pH as shown in the figure below. Which substitution would most likely cause this change? Your choices are given below. Please support your response. a) b) c) d) leucine to serine leucine to arginine leucine to tryptophan leucine to glutamate e) leucine to isoleucine Normal . Protein Mutant Protein Orlgin The purple patches of the Halobacterium halobium membrane, which contain the protein bacteriorhodopsin, are approximately 75% protein by weight and 25% lipid by weight. If the average molecular weight of protein is 26,000 and an average phospholipid has a molecular weight of 800, calculate the molar ratio of phospholipid to protein. 4.

Explanation / Answer

The movement of amino acids through a electrophoresis gel depend upon their isoelectric points. Isoelectric point is a particular pH value at which an amino acid behaves as an electrically neutral species and thus do not move from their point of origin in a gel.

An amino acid having lower than neutral isoelectric point is considered acidic and thus will have a net negative charge on them and will move towards anode( positive terminal) in a gel. An amino acid having higher than neutral isoelectric point is considered basic and will have a net positive charge and will move toward cathode ( negative terminal) in a gel.

Now Isoelectric point of

Leucine is 6.04 ( slightly acidic so move towards anode at a moderate speed)

Arginine is 11.00 ( Basic, so should not at all move towards anode, should move towards cathode)

Tryptophan is 5.88 ( slightly acidic should move toward anode at a moderate speed)

Glutamate is 3.22 ( highly acidic so should move toward anode at a higher speed)

Isoleucine is 6.04 ( same as leucine so should move toward anode at a moderate speed)

Now we can see in the image in the question the mutant variety has moved much further than the original protein ,which means that the mutant variety has much higher speed through the gel. Now judging by the isoelectric points of the amino acids in the options given we can see only Glutamate has much higher speed as compared to leucine . Therefore Glutamate must be the mutant form.

Ans is d) Leucine to glutamate

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.