Theorganization of protein subunits is the quaternary structure of the protein. Inthe quaternary structure they contain two or more polypeptide chains which areindependent in nature respectively. Quaternary structures operate only singlefunctional unit. In this aspect quaternary proteins are stabilized just the waytertiary structures are stabilized by the help of disulfide bonds and theinteractions between non-covalent tertiary proteins.
Multimers which are the multiplesubunits of polypeptides. These multimers can also be called as dimer, timer,tetramer and pentamer when they contain two, three, four and five subunits.With the help of symmetry operations these subunits are connected and relatedwith each other like in the dimer with two-fold axis. Hemoglobin is a heterotetrametricwith two alpha and beta chains. Homo and hetero tetramer are the two different subunitsmade of multimers. Proteinsare the chemical constituents from amino acids which contains an ? carbon atomat the center. This indicates from the alpha position all the subordinategroups are connected to C. It is connected to alpha proton H, side chain R inwhich different amino acids are connected, carboxylic acid and amino functionalgroup are attached respectively.
Except glycine remaining 20 amino acidscontains asymmetric carbon center and glycine contains a proton as its sidechain. The configuration for the proteins is different they have L-isomer andsynthesized on ribosome. Side chains of amino acid have unique functions fortheir biological proteins. These are classified into three different categoriessuch as nonpolar, uncharged, and charged polar. Side chains play an importantrole. Some are low soluble in water because they are formed when they show VanderWaals interaction with water molecules. Only three amino acids have aromaticrings with side chains and they are chemically reactive, hydrophobic in someconditions.
When electrons are polarized. Stabilizationand formation of Protein StructurePolypeptide ChainAmino acids areconverted to polymeric chain through dehydration synthesis by condensing aminoacids with each other. Then from the carboxylic and amino functional groupswhich are situated next to the C-N bond, a water molecule is lost. These arecalled polymerization reactions, and these are not spontaneous, but they are occurredby the energy driven action.
Ribosome helps for that reactions. For both RNAand proteins ribosomes are the complexes. Ribosome can translate a proteinsequence by converting a gene sequence in the form of messenger RNA. During thesynthesis of protein each amino acid (which are 20) is encoded by the gene.While post-translation modifications derive some amino acids and some othersare incorporated with the help of ribosomes.
Some reactions are not spontaneous.In the reverse reaction polypeptides are involved in hydrolysis. This reactionoccurs very slow due to this reason proteins are depolymerized and are stable biologicallyand chemically. Hydrolytic enzymes which facilitate the decomposition of apolypeptide chain into particularized amino acids. Most of the proteins containdifferent types of amino acids. So, they are called as heteropolymer.
Only somerare areas contain protein sequence made of few amino acids. Therefore, theyhave heterogeneous environment which are intensified by protein structures inhigher levels