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BIOL 200 (5)
Chapter 3

Chapter 3 - Protein Structure and Function

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Biology (Sci)
BIOL 200
Monique Zetka

Chapter 3Protein Structure and FunctionTypes of proteinsStructural determine shapes of cells are guide railsScaold bring other proteins together to perform functionsEnzymes catalyze chemical reactionsMembrane transport proteins permit ow of ions and molecules across membranesRegulatory signals sensors switches controlling activityMotor proteins move proteins organelles cells organismsStructure of Proteins Fold into 3D shape held together by noncovalent interactions Function comes from 3D structure 3D structure comes from aa sequence and intramolecular noncovalent interactionsPrimary Structure There are 20 amino acids Primary structure is the sequence of aas aas are linked by peptide bondbetween amino group of aa 1 and carboxyl group of aa 2Oligopeptidepeptide A short dened chain of amino acids 2030 aa longPolypeptide Longer chains 200500 residuesProtein A polypeptide with a 3D structureDalton 1 dalton1 atomic mass unitSecondary Structure Spatial arrangements of segments of polypeptide chains held together by H bonds H bonds are between backbone amide and carbonyl groupsAlpha helix Backbone forms a spiral structureCarbonyls O hydrogen bonds to amide H atom of aa 4 units down the chain toward C terminus All Hbond receptors point in the C end down 1 complete turn every 36 residues 054 nmturn Side chains point outward Proline is not found in alpha helicescant make H bonds since amino group is bound to R group Most stable and common helical form Alternatives coiled coil 35 residues and 051 nmturnBeta sheet each strand is 58 residues long H bonds are between separate strands perpendicular to R groups Align into adjacent strands making a pleated sheet Have a directionality parallel or antiparallel Found as oor of binding pockets or hydrophobic cores or hydrophilic central poresBeta turn 4 residues long On surface of a protein Reverse direction of backbone usually toward interior of protein Stabilized by Hbonds between end residues
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