Explain the process of formation of complex proteins

A protein complex or multiprotein complex — A group of two or more associated polypeptide chains.

Proteins in a protein complex are linked by non - covalent protein - protein interactions.

The process of complex formation comprises of steps namely :

1.) An encounter complex is formed that either proceeds towards final complex or dissociates again.

In this step proteins show a few specific interactions and assume many orientations.

During this phase the proteins remain largely Solvated.


2.) Productive complexes

In this step macrocollisions result into productive complex.

Tge probability of forming a productive complex can be increased by :

1.) Extending the lifetime of a macrocollisions.

2.) Influencing the site of initial contact to reduce the area that requires to be searched.

In this stage there are two mechanism that are involved.

1.) Reducing the dimension of the diffusion search

- There exists an interaction force that is non specific that keeps the macromolecules in proximity for a prolonged time thus allowing a more extensive search of the surface of the partner by transitional and rotational root.

2.) The second mechanism is the search for the binding site is limited by dipolar preorientation of the proteins upon their approach. This is mainly useful for proteins with a charge dipole.

In summary the process of formation of complex proteins is thus as follows :

1.) Encounter complex without favourable forces between the proteins is formed.

2.) Encounter complex with electrostatic attraction is created and the encounter complex is stabilized by charge interactions and the number of orientations is reduced by dipolar preorientation.

3.) The encounter complex can proceed to a more stable productive complex via a low-energy transition state.

4.) Like 3, but this time with a high-energy transition state.

5.) An electrostatic encounter complex at low ionic strength, with highly stabilized encounter complex. The proteins can get trapped in a non-productive local energy minimum. And thus a complex protein is formed.