In their quest to understand how Complex IV would 'know' if cytochrome c was loaded up with an electron and 'ready' for the binding interaction, Imai et al. (2016) provided this 'surface' rendering of the Complex IV face that binds to cytochrome c:

It is color-coded with red to and blue to indicate negatively- and positively-charged surfaces respectively. (3D shape is important as well of course, and the article established that cytochrome c undergoes a 3D shape change as it gets reduced that could help it to better fit this binding site.)

This image has a large red patch on Complex IV indicating negative charge. Which parts of cytochrome c would be most likely to interact with this?

We didn't see all of the R-groups (especially the side chains) and potential additional backbone H-bond donors/acceptors when we were shown the 'front face' of cytochrome c, and we didn't look at its overall 'face' (contouring). However when cytochrome c is loaded with an electron (i.e. in its ______ state), one of the favorable interactions might be an electrostatic interaction with ______ that interacts with the Complex IV negative charge.

Two of the residues that were shown in an earlier figure (E4 and K13) are likely to be charged - review amino acid 1-letter codes and chemistry here
Links to an external site.
as needed so that you can fill in this blank. (Which one is positively charged? Which one is negatively charged? Therefore which one should be attracted to the negatively-charged Complex IV surface?)

Question

In their quest to understand how Complex IV would 'know' if cytochrome c was loaded up with an electron and 'ready' for the binding interaction, Imai et al. (2016) provided this 'surface' rendering of the Complex IV face that binds to cytochrome c:

It is color-coded with red to and blue to indicate negatively- and positively-charged surfaces respectively. (3D shape is important as well of course, and the article established that cytochrome c undergoes a 3D shape change as it gets reduced that could help it to better fit this binding site.)

This image has a large red patch on Complex IV indicating negative charge. Which parts of cytochrome c would be most likely to interact with this?

We didn't see all of the R-groups (especially the side chains) and potential additional backbone H-bond donors/acceptors when we were shown the 'front face' of cytochrome c, and we didn't look at its overall 'face' (contouring). However when cytochrome c is loaded with an electron (i.e. in its ______ state), one of the favorable interactions might be an electrostatic interaction with ______ that interacts with the Complex IV negative charge.

Two of the residues that were shown in an earlier figure (E4 and K13) are likely to be charged - review amino acid 1-letter codes and chemistry here
Links to an external site.
 as needed so that you can fill in this blank. (Which one is positively charged? Which one is negatively charged? Therefore which one should be attracted to the negatively-charged Complex IV surface?)

BlackTom AI · Accepted Answer

Let's break down the prompt and each answer option to understand the reasoning behind the correct pair.

First, the question asks: which state of cytochrome c and which residue would interact with the negatively charged patch on Complex IV? The key ideas are:
- The Complex IV surface is negatively charged (red patch).
- An attractive electrostatic interaction would occur with a positively charged residue on cytochrome c.
- The binding context described involves cytochrome c being loaded with an electron, i.e., cytochrome c in its reduced state, which is the state that enables the proper binding interaction in this scenario.

Now evaluate each option:

Option A: oxidized ; E4
- E4 is glutamate, which carries a negative charge at physiological pH. An interaction with a negatively charged surface would be repulsive rather than attractive, so this residue would not be favored for binding the negatively charged Complex IV surface. Additionally, the question emphasizes the reduced state for proper interaction, so the oxidized state is unlikely in this context. Therefore this option is incorrect.

Option B: oxidized ; K13
- K13 refers to lysine at position 13, which is positively charged. While positive residues could in principle be attracted to a negative surface, the prompt specifies that the favorable interaction occurs when cytochrome c is reduced (not oxidized). Since the state would be oxidized here, this option misstates both the charge-interaction context and the redox state, making it incorrect.

Option C: reduced ; E4
- Here, E4 is the negatively charged glutamate residue. A negatively charged residue would be attracted to nothing but additional negative charge and would be repelled by the negative Complex IV patch, so this is not favorable. Moreover, the reduced-state requirement is not satisfied with E4 being the interactive partner in this description, so this option is incorrect.

Option D: reduced ; K13
- This combination matches the logic described: cytochrome c in the reduced state provides the appropriate electrostatic context for binding, and K13 (lysine) is positively charged, making it the residue most likely to interact with the negatively charged surface of Complex IV. This aligns with the idea of an attractive interaction between a positive charge on cytochrome c and the negative patch on Complex IV, as well as the emphasis on the reduced state for productive binding. Therefore this option is correct.

In summary, the incorrect options either pair the wrong redox state (oxidized) or pair the wrong residue (E4 is negative) or both, while the correct option uniquely satisfies both the reduced state and the positively charged residue (K13) expected to engage the negative Complex IV surface.

类似问题

Question 30 Choose a, b, c or d as the best answer. The author’s main argument is that the 100:80:100 model __________.

Write ONE OR TWO WORDS from the text to complete the sentence. 24. ‘their’ in paragraph 5 refers to Answer Question 12[input].

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