My misunderstandings about protein structure

[sameeralord]

Ok as the title suggests I want to clear up my misunderstandings on protein structure.

1. When they say primary,secondary,tertiary and quarternary structure do they mean different stages of a protein. What I mean is do all proteins have a tertiary or quarternary structure and are primary,secondary structures simply stages of them before they became a protein. Or do some proteins remain in secondary or primary structure.
2. "Myoglobin is a single-chain globular protein of 153 amino acids, containing a heme (iron-containing porphyrin) prosthetic group in the center around which the remaining apoprotein folds. It has eight alpha helices and a hydrophobic core. "(wikipedia)

Does myoglobin have 8 different polypeptide helix chains joined or is it the same chain twisted to make 8 helixes. I thought one chain could only make one helix.

"Collagen contains three different polypeptide helixes joined together"

Does this make Collagen a quarternary structure. What is the basic difference between quaternary and tertiary structure. My understanding is that tertiary structure only has one chain twisted many ways and quaternary structure has two or more different polypeptide chains. Is this wrong?

Thanks a lot for taking your time to read this. If you could help me with these basics I would be very greatful. Thank you

 

[Ygggdrasil]

Ok as the title suggests I want to clear up my misunderstandings on protein structure.

1. When they say primary,secondary,tertiary and quarternary structure do they mean different stages of a protein. What I mean is do all proteins have a tertiary or quarternary structure and are primary,secondary structures simply stages of them before they became a protein. Or do some proteins remain in secondary or primary structure.

Yes, they refer to different stages of different levels of protein structure. A good analogy is a book. You can think of a writing as having different levels of structure. At the base, there are letters (amino acids) which can be strung together into words (primary structure). These words can be of different types (secondary structure) and precise arrangments of words creates sentences (tertiary structure). You can group sentences together to make paragraphs (quaternary structure).

Now, there are proteins that lack some of these levels of structure. For example, myoglobin functions as a monomer so it lacks quaternary structure. But, myoglobin does have a tertiary structure (it's overall shape) that is formed from various helices (its secondary structural elements). I should mention, however, that there are some proteins known as intrinsically disordered proteins that lack any appreciable secondary or tertiary structure.

2. "Myoglobin is a single-chain globular protein of 153 amino acids, containing a heme (iron-containing porphyrin) prosthetic group in the center around which the remaining apoprotein folds. It has eight alpha helices and a hydrophobic core. "(wikipedia)

Does myoglobin have 8 different polypeptide helix chains joined or is it the same chain twisted to make 8 helixes. I thought one chain could only make one helix.

Myoglobin consists of a single polypeptide chain. Different regions of this chain can form separate helices (or other secondary structural elements). The specific arrangement of the helices and the amino acid chains that link these helices form the tertiary structure of myoglobin.

"Collagen contains three different polypeptide helixes joined together"

Does this make Collagen a quarternary structure. What is the basic difference between quaternary and tertiary structure. My understanding is that tertiary structure only has one chain twisted many ways and quaternary structure has two or more different polypeptide chains. Is this wrong?

That is correct. A protein will have quaternary structure if it consists two or more separate polypeptide chains.

 

[quicknote]

for reaching out and seeking clarification on protein structure. I can understand how the different levels of protein structure can be confusing at first. Let me address your questions and hopefully clear up your misunderstandings.

1. The primary, secondary, tertiary, and quaternary structures of proteins refer to different levels of organization within a protein molecule. All proteins have a primary, secondary, and tertiary structure, but not all proteins have a quaternary structure. Primary structure refers to the linear sequence of amino acids that make up a protein. Secondary structure refers to the folding and interactions between neighboring amino acids, resulting in patterns such as alpha helices and beta sheets. Tertiary structure refers to the overall 3-dimensional shape of a single protein molecule. Quaternary structure refers to the interactions between multiple protein molecules to form a larger functional unit. So, to answer your question, primary and secondary structures are stages in the formation of a protein, while tertiary and quaternary structures refer to the overall organization of a protein.

2. Myoglobin is a single chain protein, meaning it is made up of only one polypeptide chain. The eight alpha helices mentioned in the description are not separate chains, but rather different regions of the same chain that are folded and twisted to form the overall structure. This is also true for collagen, which is made up of three separate polypeptide chains that are intertwined to form a triple helix. This triple helix structure is what gives collagen its strength and stability.

The main difference between quaternary and tertiary structure is the number of polypeptide chains involved. As mentioned before, tertiary structure refers to the overall 3-dimensional shape of a single protein molecule. Quaternary structure refers to the interactions between multiple protein molecules to form a larger functional unit. This can include interactions between two or more identical chains, or between different chains, as in the case of collagen.

I hope this helps clear up your misunderstandings about protein structure. Keep asking questions and seeking clarification, as it is an important part of the scientific process. Best of luck in your studies!