Question

state the uses of complex proteins

Answer 1

Protein complex

The Bacillus amyloliquefaciens ribonuclease barnase (colored) and its inhibitor barstar (blue) in a complex

A protein complex or multiprotein complex is a group of two or more associated polypeptide chains. Different polypeptide chains may have different functions. This is distinct from a multienzyme complex, in which multiple catalytic domains are found in a single polypeptide chain.

Protein complexes are a form of quaternary structure. Proteins in a protein complex are linked by non-covalent protein–protein interactions, and different protein complexes have different degrees of stability over time. These complexes are a cornerstone of many (if not most) biological processes and together they form various types of molecular machinery that perform a vast array of biological functions. The cell is seen to be composed of modular supramolecular complexes, each of which performs an independent, discrete biological function.

Through proximity, the speed and selectivity of binding interactions between enzymatic complex and substrates can be vastly improved, leading to higher cellular efficiency. Many of the techniques used to break open cells and isolate proteins are inherently disruptive to such large complexes, so it is often difficult to determine the components of a complex. Examples of protein complexes include the proteasome for molecular degradation and most RNA polymerases. In stable complexes, large hydrophobic interfaces between proteins typically bury surface areas larger than 2500 square Ås.

Answer 2

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A Protein Complexes

Protein complexes perform all the essential biological functions such as signal transduction, cell cycle control, cell mobility and cytokinesis, DNA replication, RNA transcription, protein translation, posttranslational modification, translocation, and targeted degradation. In some of these examples, the protein levels of the entire proteome may remain relatively unchanged and yet, because of the formation or disassembly of certain protein complexes, biological processes can be initiated, modulated or terminated.

Protein folding and structural maintenance are helped greatly by interaction with molecular chaperones (Hartl, 1996). The important biological functions of chaperones make them potential targets for antibacterial drugs. This potential is illustrated by a mechanistic study, in which peptides derived from insects (previously shown to be antibacterial) were used as affinity-capture reagents. In an analysis of E. coli extracts, GroEL and DnaK were identified as the major interacting protein species (Otvos et al., 2000). Subsequent experiments demonstrated that the antibacterial peptide action was species specific, as these peptides interacted only with the bacterial chaperone DnaK and not with Hsp70, the human equivalent protein.




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