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Protein structure and function
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- 1Primary structure= sequence of amino acids N >> C
single letter codes/ standard abbreviations - 2Secondary structure= folding parts of primary sequence into particular structures
contiguous/ from different parts
alpha helix
beta sheet - 3Protein folding- The main driving force in protein folding is to attain an energetically stable structure
- Water soluble chains > hydrophobic core (must pack hydrophobic side chains into interior)
Main polypeptide chain hydrophilic (polar C=O and N-H) > must adopt structures which neutralise groups by hydrogen bonding - 4Alpha helix5-40 amino acids
N-H and C=O hydrogen bonded along axis of helix
stable
3.6 amino acids per turn (each 100 degrees rotation)
vertical distance = 0.15 nm
carboxyl group bonded to amino group 4 places ahead
side chains point out
helical wheel diagram - 5Beta sheetnon-continuous regions of polypeptide chain = beta strands
beta strands line up , hydrogen bonds between C=O group one strand and N-H groups of another
PARALLEL
hydrogen bonds evenly spaced within sheet
fully extended
same direction
ANTIPARALLEL
thinner and wider regions
fully extended
opposite direction
pleated structure - 6Loop regionssecondary structures
long loops = random coils
short loops = beta turn - beta strands
proline: locked ring structure > kink
glycine: small side chain > turns
Beta-alpha-beta motif: parallel beta strands connected by an alpha helix - crosses the beta sheet from one edge to another - 7Post-translational modificationsmodified after synthesis
secondary structure may change as features of amino acids changes
rare amino acids
sugars, carbs, glycans can be added to parts of protein
glycoprotein
lipoprotein - 8Tertiary structure= final 3d structure of protein, association of secondary structures into compact domains
bonds
non covalent
covalent: disulphide bridges - cysteine crosslink - 9Quaternary structure=formed from more than one polypeptide chain (subunits)
part of multimeric complex - 10Dimer= 2 peptide units, simplest multimeric complex
HOMODIMER
same protein
HETERODIMER
2 different polypeptides - 11Structure summaryThe primary structure of a protein is the sequence of amino acids which form the polypeptide chain and the position of any disulphide cross-links. This therefore represents all of the covalent bonds within the protein.
Different regions of the polypeptide chain then fold into regular local secondary structures, e.g. a-helices and b-sheets.
Tertiary structure is then formed by the packing of these structural elements into compact globular domains.
Some proteins contain several subunits formed from individual polypeptides arranged in a quaternary structure. - 12Protein typesGlobular and fibrous
- 13Globularcompact domains
active components
e.g. haemoglobin, antibodies, enzymes transport molecules etc - 14Fibrousprotein chains arranged into fibres
structural role
coiled-coil
beta sheets
triple helix - 15Alpha keratincoiled-coil
- 16FibroinAntiparallel beta sheet
- 17Collagentriple helix
Información
- Descripción
- (111) Year 1 BIOL Fichas sobre Protein structure and function, creado por Emily H el 05/11/2020.
- Creado por
- Emily H
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