Understanding Protein Folding and Structure

The tertiary structure of protein folding has a polypeptide chain backbone and a number of protein secondary structures: alpha helices and beta-pleated sheets. The tertiary structure is three-dimensional. The protein folding that causes the formation of the tertiary structure is influenced by hydrophobic interactions, disulfide bridges, hydrogen bonds, and salt bridges that create hydrophobic and hydrophilic regions.

The protein quaternary structure is the highest level of protein architecture and refers to the arrangement of protein subunits and their interactions with one another. There is a range in the complexity in the quaternary structure of proteins from dimers, such as DNA polymerase, to tetramers, such as hemoglobin. These structures are always composed of more than one protein subunit.

There are a number of ways that scientists study protein folding and structure. They include the following processes: mutation studies, x-ray crystallography, and spectroscopy. Mutation studies compare the folding patterns of wild type proteins and those with targeted point mutations. X-ray crystallography is a form of high-resolution microscopy that uses x-rays to study the atomic structure of protein crystals through diffraction patterns. Last, a number of spectroscopy methods are employed to study protein folding by comparing unfolded, folded, and partially folded proteins.

Quaternary protein structure is distinguished by the fact that several polypeptide chains come together to make a functional protein. This is different than the first three levels of protein structure, which only involve one polypeptide chain. Quaternary structure is held together primarily by hydrophobic interactions between the polypeptide chains (ionic and/or hydrogen bonding is often seen as well). Each polypeptide chain forms a subunit of the protein.

Disruption of normal protein folding or denaturation—protein unfolding—occurs under certain environmental conditions. Denaturation is defined as the loss of quaternary, tertiary, and secondary folding through the disruption of protein subunits and bonds. The environmental conditions that cause denaturation include the following: extreme temperatures, chemical interference, and extreme pH levels. Denatured proteins may sometimes refold if conditions stabilize; however, this does not typically happen.

Denaturation is the correct answer here. The denaturation of a protein occurs when a catalyst causes the disruption and/or destruction of the bonds in a protein structure. Heat is one of the ways to denature a protein because the heat causes the molecules to vibrate quickly and coagulate into the white substance we eat.

Secondary structure is made up of alpha helix and beta pleated sheets. Linear sequence of amino acids is found in primary structure, 3D folding is found in tertiary structure, and two peptide chains joined by non covalent bonds are found in quaternary.

The formation of beta pleated sheets and alpha helices occur in the secondary structure of a protein immediate after the sequence of the polypeptide has been formed. These two structures, alpha helices and beta-pleated sheets, are formed by the hydrogen bonds that occur among the amino acids of the polypeptide.

The formation of -helices and -pleated sheets constitute the secondary structure of a protein. These conformations are reinforced by hydrogen bonds between the atoms in the polypeptide chain.

Primary structure is determined by peptide bonds, which link adjoining amino acids in sequence. Tertiary structure is determined by disulfide bonds between cysteine residues and hydrophobic interactions. Quaternary structure is determined by interactions between multiple subunits of a protein.

Cells have certain mechanisms to protect proteins from denaturation and ensure proper folding. The cell uses two mechanisms to protect proteins: chaperones and heat shock proteins. Chaperones are a large class of proteins that aid with protein folding and prevent folding defects under normal and stressed conditions, during which chaperone expression is up regulated. Chaperones use ATP to induce a conformational change to provide an isolated environment for the protein to fold and prevent protein aggregation. Heat shock proteins are only produced under stress conditions. Heat shock proteins have a variety of functions including functioning as a chaperone, aiding in the binding of immune antigens, and preventing platelet aggregation in the cardiovascular tract.