Why and how does the proteins fold?

Answer 1

A protein is driven into its structure

by hydrophobic interactions with water. The final folding

of a protein is determined by its primary structure-by the

chemical nature of its side groups. Many proteins can be

fully unfolded ("denatured") and will spontaneously refold

back into their characteristic shape.

The stability of a protein, once it has folded into its 3-D

shape, is strongly influenced by how well its interior fits

together. When two nonpolar chains in the interior are in

very close proximity, they experience a form of molecular

attraction called van der Waal's forces. Individually quite

weak, these forces can add up to a strong attraction when

many of them come into play, like the combined strength

of hundreds of hooks and loops on a strip of Velcro. They

are effective forces only over short distances, however;

there are no "holes" or cavities in the interior of proteins.

That is why there are so many different nonpolar amino

acids (alanine, valine, leucine, isoleucine). Each has a different

sized R group, allowing very precise fitting of nonpolar

chains within the protein interior. That's

why a mutation that converts one nonpolar amino

acid within the protein interior (alanine) into another

(leucine) very often disrupts the protein's stability; leucine

is a lot bigger than alanine and disrupts the precise way the

chains fit together within the protein interior. A change in

even a single amino acid can have profound effects on protein

shape and can result in loss or altered function of the

protein.

Answer 2

Proteins fold with the assistance of chaperonins. Their structure is determined by their primary and secondary structure, as well as hydrophobic interactions.

Answer 3

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