It is not easy to make a list of proteins. To create a list there is a need to define the use of these proteins. In nature, the amount of different proteins is sheer endless. While focusing on human aging it is important to focus only on proteins which fulfill a role in this. The enclosed list does not pretend to be complete but can be used as a guideline for further work ;
|Globular proteins||Plasma proteins / Serum Amyloid P Component
Serum albumin / Coagulation factors
Complement proteins / C1-inhibitor
C3-convertase / Factor VIII / Factor XIII
Protein C / Protein S / Protein Z / Protein Z-related protease inhibitor
Thrombin / Von Willebrand Factor
Acute phase proteins
C-reactive protein / Hemoproteins
Hemoglobin (oxyhemoglobin and deoxyhemoglobin)
Cadherin / Ependymin / Integrin
NCAM / Selectin
|Transmembrane transport proteins
|CFTR / Glycophorin D
Scramblase / Ion channels
Ligand-gated ion channels
Nicotinic acetylcholine receptor
GABAa receptors / Voltage-gated ion channels
Potassium channels / Calcium channels
Synport / Antiport proteins / Glucose transporter
|Hormones and growth factors||Colony-stimulating factors (CSFs)
Epidermal growth factor (EGF)
Fibroblast growth factor (FGF)
Platelet-derived growth factor (PDGF)
Transforming growth factors (TGFs)
Vascular endothelial growth factor (VEGF)
Peptide hormones / Insulin
Insulin-like growth factor (IGF) / Oxytocin
|Extracellular matrix proteins||Collagen / Elastin / F-spondin / Pikachurin
The best way to separate proteins is based on structure. It is possible to distinguish 4 different structures which are leading at all time.
The first level of structure in amino acids is a polypeptide chain. The primary structure is held together by peptide bonds in which the two ends of the polypeptide chain are referred to as the carboxyl terminus (C-terminus) and the amino terminus (N-terminus) based on the nature of the free group on each extremity. When a peptide bond is formed, a water molecule is lost. For example, insulin is composed of 51 amino acids in 2 chains. One chain has 31 amino acids, and the other has 20 amino acids. Post-translational modification such as disulfide bond formation, phosphorylations, and glycosylations are usually also considered a part of the primary structure.
There are two main types of secondary structure, the α-helix, and the β-strand or β-sheets. These secondary structures are defined by patterns of hydrogen bonds between the main-chain peptide groups. They have a regular geometry due to interactions between atoms of the backbone constrained to specific values of the dihedral angles ψ and φ on the Ramachandran plot. Several sequential secondary structures may form a “supersecondary unit”. Some parts of the protein may look in disorder. Many proteins contain both α helices and β pleated sheets. Proline is found in unstructured regions between secondary structures. The amino acids tryptophan, tyrosine, and phenylalanine have large ring structures in their R groups and found in β pleated sheets, probably the β pleated sheet structure provides enough of space for side chains.
Tertiary structure refers to the three-dimensional structure of monomeric and multimeric protein molecules. α-helixes and β-pleated-sheets are folded into a compact globular structure A tertiary structure is primarily due to interactions between the R groups of the amino acids. Folding is driven by the non-specific hydrophobic interactions. The structure is stable only when parts of a protein domain are locked into place by specific tertiary interactions, such as salt bridges, hydrogen bonds, and the tight packing of side chains and disulfide bonds. The disulfide bonds are extremely rare in cytosolic proteins since the cytosol (intracellular fluid) is generally a reducing environment.
This is the three-dimensional structure consisting of the aggregation of two or more individual polypeptide chains (subunits) that operate as a single functional unit. Complexes of two or more polypeptides (i.e. multiple subunits) are called multimers. It would be called a dimer if it contains two subunits, a trimer if it contains three subunits, a tetramer if it contains four subunits, and a pentamer if it contains five subunits. The subunits are frequently related to one another by symmetry operations, such as a 2-fold axis in a dimer. Multimers made up of identical subunits are referred to with a prefix of “homo-” (e.g. a homotetramer) and those made up of different subunits are referred to with a prefix of “hetero-“, for example, a heterotetramer, such as the two alpha and two beta chains of hemoglobin.
Now the main target names are clarified, content, structure and chemical formulas of the following products it is easier to understand the value and use of it in the digestive and metabolic system. The daily food contains all needed amino acids/proteins in specific quantities and should not need to have lack of anything. But during aging, it seems to create insufficient availability of needed nutrients. The first step is to identify some important forms of proteins in dairy foods. This gives inside information and understanding of digestion.