Infrared spectroscopy of proteins.

Role of plant heat-shock proteins and molecular chaperones in the abiotic stress response

"Natively unfolded" proteins occupy a unique niche within the protein kingdom in that they lack ordered structure under conditions of neutral pH in vitro. Analysis of amino acid sequences, based on the normalized net charge and mean hydrophobicity, has been applied to two sets of proteins: small globular folded proteins and "natively unfolded" ones. The results show that "natively unfolded" proteins are specifically localized within a unique region of charge-hydrophobicity phase space and indicate that a combination of low overall hydrophobicity and large net charge represent a unique structural feature of "natively unfolded" proteins.

Why are "natively unfolded" proteins unstructured under physiologic conditions?

This review deals with current concepts of vibrational spectroscopy for the investigation of protein structure and function. While the focus is on infrared (IR) spectroscopy, some of the general aspects also apply to Raman spectroscopy. Special emphasis is on the amide I vibration of the polypeptide backbone that is used for secondary-structure analysis. Theoretical as well as experimental aspects are covered including transition dipole coupling. Further topics are discussed, namely the absorption of amino-acid side-chains, 1H/2H exchange to study the conformational flexibility and reaction-induced difference spectroscopy for the investigation of reaction mechanisms with a focus on interpretation tools.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033583502003815

What vibrations tell us about proteins

The experimental material accumulated in the literature on the conformational behavior of intrinsically unstructured (natively unfolded) proteins was analyzed. Results of this analysis showed that these proteins do not possess uniform structural properties, as expected for members of a single thermodynamic entity. Rather, these proteins may be divided into two structurally different groups: intrinsic coils, and premolten globules. Proteins from the first group have hydrodynamic dimensions typical of random coils in poor solvent and do not possess any (or almost any) ordered secondary structure. Proteins from the second group are essentially more compact, exhibiting some amount of residual secondary structure, although they are still less dense than native or molten globule proteins. An important feature of the intrinsically unstructured proteins is that they undergo disorder–order transition during or prior to their biological function. In this respect, the Protein Quartet model, with function arising from four specific conformations (ordered forms, molten globules, premolten globules, and random coils) and transitions between any two of the states, is discussed.

/pdf/natively-unfolded-proteins-a-point-where-biology-waits-for-2p9xoup1zq.pdf

Natively unfolded proteins: a point where biology waits for physics.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2895%2900775-5

Temperature-induced exposure of hydrophobic surfaces and its effect on the chaperone activity of α-crystallin

Molecular Chaperone-like Properties of an Unfolded Protein, αs-Casein

Temperature-dependent Chaperone Activity and Structural Properties of Human αA- and αB-crystallins

http://www.jbc.org/content/279/27/28539.full.pdf

A novel salt-tolerant L-myo-inositol-1-phosphate synthase from Porteresia coarctata (Roxb.) Tateoka, a halophytic wild rice: molecular cloning, bacterial overexpression, characterization, and functional introgression into tobacco-conferring salt tolerance phenotype.

Kali P. Das

Papers

Temperature-induced exposure of hydrophobic surfaces and its effect on the chaperone activity of α-crystallin

Molecular Chaperone-like Properties of an Unfolded Protein, αs-Casein

Temperature-dependent Chaperone Activity and Structural Properties of Human αA- and αB-crystallins

A novel salt-tolerant L-myo-inositol-1-phosphate synthase from Porteresia coarctata (Roxb.) Tateoka, a halophytic wild rice: molecular cloning, bacterial overexpression, characterization, and functional introgression into tobacco-conferring salt tolerance phenotype.

Role of ATP on the Interaction of α-Crystallin with Its Substrates and Its Implications for the Molecular Chaperone Function