tertiary structure (domains)

what is tertiary structure of the protein?

unique three-dimensional conformations that globular proteins assume as they fold into their native (biologically active) structures and prosthetic groups

what is Protein folding?

process in which an unorganized, nascent molecule acquires a highly organized structure, occurs as a consequence of the interactions between the molecule’s side chains

tertiary structure feutures?

1) polypeptides fold in such a fashion that amino acid residues distant [far] from each other in the primary structure come into close proximity

2)globular proteins are compact as water molecules are excluded from the interior making interactions between polar and non-polar possible

3)large globular proteins have domains (part of the tertiary structure that have specific function inside the chain)

THE CORE OF THE DOMAIN IS CALLED FOLD

4)a number of proteins are modular / mosiac proteins by which they contain duplicate or imperfect copies of one or more repeating domains linked in a series e.g: 1-fibronectine can bind to collagen and proteoglycans

2- immunoglobins

type and examples of domains:

1. Types :

   1. Alpha domains : made only of alpha helices

   2. Beta domains : made only of antiparallel beta strands

   3. A/B domains : made up of a mix between the two

2. Examples

   1. EF hand

   2. Leucine zipper

   3. B barrel

   4. ATP binding domain of hexokinase

   5. a/b zinc binding motif

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EF hand, a type of A-domains it is helix-loop-helix that binds specifically to Ca2+

l?

leucine zipper

DNA binding domain are example of α-domains.

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Human retinol-binding protein, a type of β-barrel domain

(retinol, a visual pigment molecule is shown in yellow

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The ATP-binding domain of hexokinase, a type of α/β-domain.

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The α/β zinc-binding motif, a core feature of numerous DNA binding domains.

types of interactions stabilize tertiary structure

1- Hydrophobic interactions [non polar-non polar]

2-Electrostatic interactions. [salt-bridge , opposite charged ions , cavalent ] strongest type

3- Hydrogen bonds [between polar amino acids] 6

4- covalent bonds (disulfide bonds)

5- hydration water-bridge