User:Bhatchhetrbb/sandbox

Protein

Proteins are one of the most important versatile molecules found in living organisms. It has varieties of functions such as enzyme catalyst, acts as transporter for ions and molecules, regulating cellular and physiological activities and many more. Protein comprised of 20 different amino acids connected each other by peptide bonds. Naturally occurring 20 different types of amino acids are studied in DNA sequencing. Amino acids are joined side by side during protein synthesis to form chain, called peptide bond.

Structure of Protein

Proteins are composed of polymers of amino acids and which are joined each other by polypeptide bonds. Each protein is built from different amino acids and also form a complex structure by combination of two proteins. Structurally, there are four different types of protein. i.e. primary, secondary, tertiary and quaternary.

i. Primary structure is based on sequence of amino acids in a polypeptide chain.

ii. Secondary structure is based on hydrogen bond with many loops, alpha helix and beta sheet.

iii. Tertiary structure is formed by non local interaction disulfide bonds, salt bridges and hydrophobic core perform basic fundamental functions.

iv. Quaternary structure is formed by many polypeptide chains subunits. Also called complex protein.

 

Tyrosinase Protein Tyrosinase is type-3 copper protein widely distributed in bacteria, fungi, plants, invertebrates, and mammals. In human tyrosinase (hTyr) is an enzyme that catalyzes melanin production in melanosome'. It plays significance role in biosynthesis of melanin''' pigment which is responsible for the color of skin, hair and eyes in metazoans. Mutation in tyrosinase gene resulting the oculocutaneous albinism (OCA). Decreased and increased production of Tyrosine brings multiple disorder in human beings. The gene for tyrosinase is regulated by the microphthalmia-associated transcription factor. If tyrosine production is uncontrolled in human, melanin synthesis will be increased causing skin disorder called melasma.

Structure

Tyrosinase from different species are diverse in terms of their structural properties, tissue distribution, and cellular location. The enzyme found in fungi, plants and animal tissues are varies on the basis of their size, structure, glycosylation pattern and activation characteristics. Basically, overall structure of tyrosinase is consists of three domains.ie.,central, N-terminal and C-terminal. The central domain is made up of six conserved histamine residues with two oxidizing ions of CuA and CuB. The CuB site exhibits more conservation then CuA. Among the three copper catechol oxidases perform diphenolase activity and hemocyanins carries oxygen through haemolymph in arthropods and mollucs.



Evolution of Tyrosinase

The origin and early evolution of tyrosinase is not well understood. The type-3 copper protein family are preform various biological function including pigment formation, innate immunity and oxygen transport. The combine genetic phylogenetic and structural analysis concluded that the original type-3 copper protein possessed a single peptide and grouped into α subclass. The ancestral protein gene underwent to two duplication ie., first one prior to divergence of unknot eukaryotic lineage and second one before diversification. The prior duplication gave rise to cytosolic form(β) and latter duplication gave membrane bound form(Γ). The structural comparison concluded that active site of α and Γ forms are covered by aliphatic amino acids and β form covered with aromatic residue. Thus, the evolution of these gene family is the lineage of multicellular eukaryotes due to loss of one or more of these three subclasses and lineage specific expansion of one or both of the remaining subclasses.

References