Primary and Secondary Structure of Protein
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The document discusses the primary structure of proteins, which refers to the specific sequence of amino acids in a polypeptide chain. Amino acids are linked together by peptide bonds to form the primary structure. The different arrangements of amino acids give rise to different protein structures and functions. The primary structure determines the overall shape and conformation of a protein.
Primary and Secondary Structure of Protein
- 2. Primary structureofproteinrefers tothesequence of aminoacidspresent ina polypeptidechain. Aminoacidsare covalentlylinkedby peptidebond. Each componentin aminoacid ina polypeptideis called “residue”. Thedifferentarrangementofaminoacidsyielddifferent structure withdifferentfunctionsand activities. It determinestheshapeor conformation,intowhich a proteincan bearranged.
- 3. Methionineenkephalin ◦ Try-Gly-Gly-Phe-Leu Leucineenkephalin ◦ Try-Gly-Gly-Phe-Leu
- 4. To predict the 2nd and 3rd structure from sequence homologies withrelated proteins. Many geneticdiseases result from abnormal amino acid sequences. To understandthe molecular mechanismof action in protein. To trace evolutionary paths.
- 5. Insulin– the first protein in which the sequenceof amino acids was determined. some insulinfrom animals is biologically active in humansand can be used for treatment. And insulinfrom humans,differs slightlyby one, two, or three aminoresidues in chain A.
- 7. The regulararrangementor coilingofsegmentsofprotein chains. A uniquethree-dimensionalshapeofeach proteinwhich is importanttoitsfunction. Itis theconformationor the shape ina relativelysmallor localizedregion ofa polypeptide molecule. Secondary structures haverepetitiveinteractionresulting fromhydrogen binding betweentheamideN – H and the carbonylgroups of thepeptidebackbones.
- 8. α Helix •Coiling of the protein chain in the shape of a right-handed helix. e.g α keratin. •The C=O oxygen of anamino acid residue is H-bonded to the N-H hydrogen of the 4th amino acidresiding further down the polypeptide chain.
- 9. α- Helix
- 10. β pleated sheet – a side by side alignment of adjacent polypeptide chains. ◦ H- bondingoccurs betweenC=O oxygenofone chainandtheN-Hhydrogenofan adjacent. Thesheet conformation permits the stacking of sheets one ontop of the other.
- 11. Two Types ofβpleated sheet
- 12. β bends – permits the changein direction of a peptide chain to get a folded structure. - It gives proteins globularity rather than linearity.
- 13. TripleHelix – right handedsuper helix by the right-handed coiling of three polypeptide chain. Collagen– most abundant protein in mammals. - Constitutes the major portion of tendons and ligaments. - Important constituent ofskin. Vitamin Cis required in the formation of collagen, particularly in the hydroxylation of proline to form hydroxyproline to stabilize the structure ofcollagen.