©1999 timothy g. standish bielkoviny, enzýmy protein structure július cirák

©1999 Timothy G. Standish

Bielkoviny, enzBielkoviny, enzýmyýmy

Protein Structure

Július Cirák


Polar

BasicAcid

?

AcidAmine

Different Amino Acid ClassesDifferent Amino Acid Classes

OH

O

H

H2N

C

C

R

Generic

Non-polar

C

C

C

OH

H

H

O

H+N

H

H2N

CNH

C

C

Histidine

H

H2N

C

C

H

H

O

OH

O

C

OH

C

Aspartic acid

C

C

C

OH

H

H

O

HS

H

H2N

Cysteine

OH

H

H

O

H

H

H2N

C

C

C

Alanine

Protein Structure


Levels Of Protein OrganizationLevels Of Protein Organization Primary Structure - The sequence of amino acids in the

polypeptide chain Secondary Structure - The formation of helices and

pleated sheets due to hydrogen bonding between the peptide backbone

Tertiary Structure - Folding of helices and sheets influenced by R group bonding

Quaternary Structure - The association of more than one polypeptide into a protein complex influenced by R group bonding

Protein Structure


Levels Of Protein OrganizationLevels Of Protein OrganizationPrimary StructurePrimary Structure

Met-Gly-Ala-Pro-His-Ile-Asp-Glu-Met-Ser-Thr-...

The sequence of amino acids in the primary structure determines the folding of the molecule.

Protein Structure


Protein Secondary StructureProtein Secondary Structure

The peptide backbone has areas of positive charge and negative charge

These areas can interact with one another to form hydrogen bonds

The result of these hydrogen bonds are two types of structures: helices pleated sheets

Protein Structure


+-

Protein Secondary Structure:Protein Secondary Structure: Helix Helix

C

O

OHCN

H

HH

C

HO H

C

H

O

CN

H

HH

C

H H

CHN

C

OC

HN

OC

COC

HN

C HN

COC

OCO

C

OC

HN

H

N

CHN

Protein Structure


Protein Secondary Structure:Protein Secondary Structure: Helix Helix

R

RR

R

R

R

R

RR

R R

RR

R

R groups stick out from the helix influencing higher levels of protein organization

Protein Structure


Protein Secondary Structure:Protein Secondary Structure: Pleated Sheet Pleated Sheet

NH

C

O

C

H

CC

N

O

NH

C

O

C

H

CC

N

O

NH

C

O

C

H

CC

N

O

NH

C

O

C

H

CC

N

O

NH

C

OC

H

CCN

ONH

C

OC

H

CCN

ONH

C

OC

H

CCN

ONH

C

OC

H

CCN

O

Protein Structure


Protein Secondary Structure:Protein Secondary Structure: Pleated Sheet Pleated Sheet

NH

C

O

C

H

CC

N

O

NH

C

O

C

H

CC

N

O

NH

C

O

C

H

CC

N

O

NH

C

O

C

H

CC

N

O

NH

C

O

C

H

CC

N

O

NH

C

O

C

H

CC

N

O

NH

C

O

C

H

CC

N

O

NH

C

O

C

H

CC

N

O

NH

C

OC

H

CCN

ONH

C

OC

H

CCN

ONH

C

OC

H

CCN

ONH

C

OC

H

CCN

O

Protein Structure


Levels Of Protein OrganizationLevels Of Protein OrganizationTertiary StructureTertiary Structure

Tertiary structure results from the folding of helices and pleated sheets

Factors influencing tertiary structure include: Hydrophobic interactions Hydrogen bonding Disulphide bridges Ionic bonds

Protein Structure


Globular and Fibrous Globular and Fibrous

e.g. haemoglobin 3º structure normally

folds up in a ball hydrophilic R groups

point outwards Hydrophobic R groups

point inwards soluble metabolic functions

e.g. collagen 2º structure does not

fold up, form fibres not surrounded by

hydrophilic R groups

insoluble structural functions

Protein Structure


Hydrophobic interactionsHydrophobic interactions

Protein Structure

Valine

OH

O

H

H2N

C

C

H3C CH3

H

C

Proline

OH

O

H

H2N+

C

CH2C

CH2H2C

OH

O

H

H2N

C

C

H

Glycine


Hydrogen BondingHydrogen Bonding

Asparagine

H

H2N

C

C

H

H

O

OH

O

C

NH2

C

Glutamine

H

H2N

C

C

H

H

O

OH

O

C

NH2

C

C

H

H

N-------H (+) (-) O -------C slightly slightly

Protein Structure


Disulphide bridgesDisulphide bridges

Cysteine

C

C

C

OH

H

H

O

HS

H

H2N

Cysteine

C

C

C

OH

H

H

O

HS

H

H2N

Cysteine

C

C

C

OH

H

H

O

S

H

H2N

Cysteine

C

C

C

OH

H

H

O

S

H

H2N

Protein Structure


Ionic BondsIonic Bonds

Glutamicacid

H

H2N

C

C

H

H

O

OH

O

C

O-

C

C

H

H Arginine

OH

O

H

H2N

C

C

H

H C H

H

C

C

H

H

H

N+H2N

NH2

C

Protein Structure


e.g.G-3-P Dehydrogenasee.g.G-3-P DehydrogenaseTertiary StructureTertiary Structure

Picture source: SWISS-PROTProtein Structure


Collagen is a fibrous protein made of 3 polypeptide helices held together by hydrogen bonding

Every 3rd amino acid in the chain is a glycine (very small to let the chains lie close to each other)

Collagen molecules are found side by side forming fbres

The staggered ends help to give collagen fibres great tensile strength

Protein Structure


Levels Of Protein OrganizationLevels Of Protein OrganizationQuaternary StructureQuaternary Structure

Quaternary structure results from the interaction of independent polypeptide chains

Factors influencing quaternary structure include: Hydrophobic interactions Hydrogen bonding The shape and charge distribution on amino

acids of associating polypeptides

Protein Structure


HaemoglobinHaemoglobin



HaemoglobinHaemoglobin Haemoglobin is a globular protein with a

prosthetic ‘iron’ group

In adults, hemoglobin is made up of 4 polypeptides (2 polypeptide chains and 2 polypeptide chains)

Each polypeptide surrounds a prosthetic ‘haem’ group

Hydrophobic interactions between side groups pointing inwards maintain the structure

Hydrophilic side chains point outwards making it soluble

Fe

Protein Structure


G-3-P DehydrogenaseG-3-P Dehydrogenasefrom Bacillus stearothermophilusfrom Bacillus stearothermophilus



Sickle Cell AnaemiaSickle Cell Anaemia

Protein Structure


E + S → ES → EP → E + P

©1999 timothy g. standish bielkoviny, enzýmy protein structure július cirák

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