Proline and Protein structure

[Obi Wan]

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Hi everyone,

I was going through the Examkrackers biology review, and they mentioned that proline disrupts alpha helix/beta pleated sheet formation due to inducing turns/bends in the protein strucure.

But in an explanation to a later question, they claim that proline only affects the tertiary structure of a protein. Shouldn't the answer be secondary structure, since it affects alpha helix/beta sheet formation?

Thanks!

 

[matth87]

A protein can be made up of multiple alpha helices and beta sheets. All these helices and sheets have to be connected some how. If the proline was found in the strand of AA's that connect 2 of them together it would be considered to affect tertiary structure, not secondary.

 

[Charles_Carmichael]

From what I understand (based on how I learnt it in biochem), turns and loops are also considered part of the secondary structure and not the tertiary structure.

I guess the answer was tertiary because changes in these secondary structures in turn affect the teritiary structure; ie. adding in a proline in a loop to induce a B-turn could also have a significant effect on the tertiary structure. I'm not sure about their statement that proline only affects tertiary structure though, because it does disrupt secondary structure as well. And proline does affect secondary structures in the sense that some secondary structures (ie. the bends) need proline in order to induce a bend. There are a number of errors in the EK books, so this might be one of them.

 

[Doodl3s]

This raises a good point for me about the distinction between 2nd and 3rd structure.
1st = AA sequence, 4th= multiple subunit structure...
2nd is supposed to be alpha vs. beta sheets... while 3rd is the big structure that these alpha and beta sheets make up... So, those bends kinda come in between...

 

[zooka]

I think for this specific question, the reason the answer was Tertiary structure, is because (at least in my book) the question is worded: " Proline creates a bend in the polypeptide chain. This phenomenon assists in the creation of what level of protein structure". Proline does disrupt secondary structure, but in doing so, it helps to form the tertiary structure with bending.

I'm not sure how positive I am, or whether or not this answer is accurate, but it seems to me, that this is why the person who wrote the question chose this answer.

 

[repititionition]

Bump from someone who also had trouble with this question.

The question (in my edition) says "Due to the ring structure of proline, it CANNOT conform to the geometry of the a-helix and creates a bend in the polypeptide chain."

The emphasis is mine, and is the reason that the answer is tertiary. I've always associated proline with the requisite steep angles of a beta turn, and chose secondary. The subtule but crucial distinction here is that proline is being discussed in the context of alpha helices, and a disruption to the alpha helix is a determinant of tertiary structure.

Hope this helps someone prepping in the future who has not had biochem and is looking for a concise (?) answer.

 

[MedGrl@2022]

From what I understand (based on how I learnt it in biochem), turns and loops are also considered part of the secondary structure and not the tertiary structure.

I guess the answer was tertiary because changes in these secondary structures in turn affect the teritiary structure; ie. adding in a proline in a loop to induce a B-turn could also have a significant effect on the tertiary structure. I'm not sure about their statement that proline only affects tertiary structure though, because it does disrupt secondary structure as well. And proline does affect secondary structures in the sense that some secondary structures (ie. the bends) need proline in order to induce a bend. There are a number of errors in the EK books, so this might be one of them.

I think I have noticed some in their audio osmosis... has anyone else found some too? It is frustrating... I am glad I can figure most of them out and not just use EK to learn everything...

 

[MedGrl@2022]

Hi everyone,

I was going through the Examkrackers biology review, and they mentioned that proline disrupts alpha helix/beta pleated sheet formation due to inducing turns/bends in the protein strucure.

But in an explanation to a later question, they claim that proline only affects the tertiary structure of a protein. Shouldn't the answer be secondary structure, since it affects alpha helix/beta sheet formation?

Thanks!

just curious what question number is this? Is this a question from a lecture or one of their in class exams? I want to check it out too.

Thanks!

 

[Temperature101]

just curious what question number is this? Is this a question from a lecture or one of their in class exams? I want to check it out too.

Thanks!

I think it's from bio 1001...

 

[repititionition]

The question I referenced is one of the in-chapter quizzes rom the "MCAT Biology" book, chapter 1.