Question

Structure and function of

transthyretin

mucin 2

catalase

calmodulin

Thanks

Answer 1

Transthyretin is a transport protein in the serum and cerebrospinal fluid that carries the thyroid hormone thyroxine (T4) and retinol-binding protein-bound to retinol.
Structure - TTR is a 55kDa homotetramer with a dimer of dimers quaternary structure that is synthesized in the liver, choroid plexus, and retinal pigment epithelium for secretion into the bloodstream, cerebrospinal fluid, and the eye, respectively. Each monomer is a 127-residue polypeptide rich in beta-sheet structure. Association of two monomers via their edge beta-strands forms an extended beta-sandwich.

Mucin 2 gene encodes a member of the mucin protein family. The protein encoded by this gene, also called mucin 2, is secreted onto mucosal surfaces. Mucin 2 is particularly prominent in the gut where it is secreted from goblet cells in the epithelial lining into the lumen of the large intestine. There, mucin 2, along with small amounts of related-mucin proteins, polymerizes into a gel of which 80% by weight is oligosaccharide side-chains that are added as post-translational modifications to the mucin proteins.
Structure - The mucin 2 protein features a central domain containing tandem repeats rich in threonine and proline that varies between 50 and 115 copies in different individuals.

Catalase - Hydrogen peroxide is a harmful byproduct of many normal metabolic processes; to prevent damage to cells and tissues, it must be quickly converted into other, less dangerous substances. To this end, catalase is frequently used by cells to rapidly catalyze the decomposition of hydrogen peroxide into less-reactive gaseous oxygen and water molecules.
Structure - Human catalase forms a tetramer composed of four subunits, each of which can be conceptually divided into four domains. The extensive core of each subunit is generated by an eight-stranded antiparallel b-barrel (b1-8), with nearest neighbor connectivity capped by b-barrel loops on one side and a9 loops on the other. A helical domain at one face of the b-barrel is composed of four C-terminal helices (a16, a17, a18, and a19) and four helices derived from residues between b4 and b5 (a4, a5, a6, and a7).

Calmodulin - The general function of CaM is to bind calcium ions and then bind a target protein, affecting its activity. The binding of calcium is achieved by the 4 EF-hand domains. A basic EF hand consists of two perpendicular alpha helices with a 12-residue loop region between them.
Structure - Calmodulin is a small, highly conserved protein that is 148 amino acids long. The protein has two approximately symmetrical globular domains each containing a pair of EF-hand motifs (the N- and C-domain) separated by a flexible linker region for a total of four Ca2+ binding sites.