أحمد محمود عيد 30104201601066

Kafrelsheikh University

Faculty of physical Therapy

االسم/هاجر أحمد محمود عيد

الفرقه/األولي

كود الطالب/‏‎6160615615655161‎

الرقم القومي/‏‎15650156156511‎

عنوان البحث )Title(

Levels of protein structure and different diseases related to protein

misfolding

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Amino acids are the fundamental units of the proteins.

There are 300 amino acid occur in nature .only 20 of them occur in

mammalian proteins.

Other amino acids are found in a number of natural proteins.

Amino acid structure

Each amino acid has the following 4 groups or atoms attached to alpha

carbon atom.

1- Amino group

2- Carboxyl group

3- Hydrogen atom

4-Side chain or radical group

Proteins

Proteins are macromolecules formed of amino acids united together by

peptide bonds.

20 Amino acid are commonly found in proteins, in different proportions

are formed of two or more polypeptide chains.

The term protein is applied to describe molecules greater than 50 amino

acid

Molecules contain less than 50 amino acids are termed peptides

The 20amino acids characterized by:

-1They are all alpha amino acids (the amino group is attached to the alpha

carbon,next to the carboxyl group), except proline. Proline is not a

typical amino acid it is an imino acid as it contains imino group –NH

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-2 The alpha carbon in all amino acid is asymmetric except glycine any

substance containing asymmetric carbon atom shows optical activities

-3 They are all L-amino acids having their (-NH2) groups towards the

left D-amino acids found only in bacterial cell wall

Amphoteric properties

Amino acids are amphoteric molecules They have both basic and acidic

groups

Zwitter ion structure

Each amino acid has its own pH at which it carries both equal negative

(COO-) and positive (NH3+) charges,thus the overall molecule is

electrically neutral

This pH called

Isoelectric point

(pl) and the amino acid at that pH is termed

Zwitter ion

Amino acid

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Amino acids classification

1-Chemical classification

Based upon the amino avid side chain (R radical)

Name Symbol Structural formula

Aliphatic non polar side chain

Glycine Gly(G)

Alanine

Ala(A)

Valine

Val(V)

Leucine

Leu(L)

Iso leucine

IIe(I)

Phenylalanine

Aromatic side chain

Phe(F)

Tyrosine

Tyr(Y)

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Tryptophan

Trp(W)



Cysteine

Sulphur-containing side chain

Cys(C)

Methionine

Met(M)

Asparagine

Acidic side chain

Asn(N)

Glutamine

Gln(Q)

Asparagine

Amidic side chain

Asn(N)

Glutamine

Gln(Q)

Lysine

Basic side chain

Lys(k)

Arginine

Arg(R)

Histidine

His(H)

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Serine

Threonine

Hydroxyl-containing side chain

Ser(S)

Thr(T)

Nitritional or biological classification:

Based upon whether the ring aids synthesized in Bady Or Not

Essential amino acids

Those are not synthesized in the body and must be supplied in diet

Their deficiency will affect the normal growth and health.

The 9 essential amino acids are: histidine, isoleucine, leucine, lysine,

methionine, phenylalanine, threonine, tryptophan, and valine

Nonessential amino acid

Nonessential means that our bodies produce an amino acid, even if we do

not get it from the food we eat. Nonessential amino acids include:

alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid,

glutamine, glycine, proline, serine, and tyrosine

Metabolic classification: Based upon the fate (metabolism) of the amino

acids inside the body.

A. Ketogenic amino acid: This amino acid can be metabolized to ketone

bodies (Leucine and lysine)

B. Mixed amino acids (Ketogenic and Glucogenic): Those amino acids

can be metabolized to both glucose and ketone bodies (Threonine,

isoleucine, phenylalanine, tyrosine, and tryptophan).

C. Glucogenic amino acids: Those amino acids can be metabolized to

glucose (The remaining amino acids)

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Function of amino acids:

6- Body peptides and proteins: e.g. plasma proteins, tissue proteins

1-Hormones: some hormones are amino acid derivatives e.g. thyroxin

3- Amines: Some amino acids give corresponding amines by

decarboxylation e.g. histidine gives histamine which is vasodilator

4-. Neurotransmitters: Some amino acids as glycine and glutamate act as

neurotransmitters

5-. Detoxication: Some amino acids are used in detoxication reactions eg

- glycine.

6- Health and growth: Essential amino acids support growth in infants

and maintain health in adults

Peptides

Peptides are compounds, formed of less than 50 amino acids link together

by peptide bonds

1- Dipeptide (2 amino acids and one peptide bond)

2- Tripeptide (3 amino acids and 2 peptide bonds).

3-Oligopeptide (4-10 amino acids).

4-Polypeptide (11-50 amino acids).

Peptide bond

It is a covalent bond formed between the carboxyl group of one amino

acid and the a - amino group of another. It is formed by removal of

water. Peptide formation needs energy, getting it from hydrolysis of a

high energy phosphate compound e.g. ATP.

Formation of a Dipeptide

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The primary structure

It is the linear sequence of amino acid residues joined through peptide

bonds to form a polypeptide chain The peptide bonds are responsible for

the primary structure. It is a covalent bond

Each polypeptide chain starts on the left side by free amino group of the

first amino acid. It is termed N - terminal (or N - terminus) amino acid.

Each polypeptide chain ends on the right side by free carboxyl group of

the last amino acid termed C - terminal (or C - terminus) amino acid. The

remaining amino acids in the chains are termed: amino acids residues

(subunits) No other forces or bonds other than peptide bonds

Secondary structure

Secondary structure results from interaction of neighbor amino acid

residues (first and fourth) Hydrogen bonds are responsible for secondary

structure (in addition to the fracture of the peptide bond) It is the bond

between the hydrogen of -NH group of one amino acid residues and the

carbonyl oxygen (C =O) of other.

There are 2 main types of secondary structure of proteins:

A. ˈɑ - helix structure: It is rod - like structure with the peptide bonds

coiled tightly inside and the side chains of residues (R) extending

outward from the chain

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Tertiary structure of protein

This is the final arrangement of a single polypeptide chain resulting from

spatial relationship of more distant amino acid residues Interaction

between different regions of the chain in secondary structure

There are two forms of tertiary structures

-6 Fibrous: which is extended form e.g. collagen, elastin and ɑ keratin

2- Globular: which is compact form and results from folding of

polypeptide chain e.g. myoglobin

There are number of different types of bonding involved

1-Peptide bond

2- Disulfide bonds (covalent and strong): between cysteine residues w

the chain

3- Hydrogen bonds (weak bond): within the chains or between chains

4- lonic bonds: between oppositely charged groups in the side chains

amino acids

5- Hydrophobic bonds: between the non - polar side chains (R) of

neutral amino acids.

Quaternary structure of protein

Many proteins are composed of several polypeptide chains. Each

polypeptide chain is called subunit. Each subunit has its own primary,

secondary and tertiary structure.

Maintained by non - covalent inter - chain bonds of the same types that

maintain tertiary structure. Examples: (Insulin: 2 subunits LDH enzyme

4 subunits, Globin of hemoglobin: 4 subunits)

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Ehlers - Danlos syndrome (EDS): This disorder is a heterogeneous

group of generalized connective tissue disorders that result from

inheritable defects in the metabolism of fibrillar collagen molecules.

EDS can result from a deficiency of collagen - process - ing enzymes (for

example, lysyl- hydroxylase deficiency or pro - collagen peptidase

deficieney), Collagen containing mutant chains is not secreted, and is

either degraded or accumulated to high levels in intracellular

compartments. Because collagen type III is an important component of

the arteries, potentially lethal vascular

problems occur.

Osteogenesis imperfecta OI: (brittle bone syndrome)

It is also a heterogeneous group of inherited disorders distinguished by

bones that easily bend and fracture

, Retarded wound healing and a rotated and twisted spine leading to

"humped - back" appearance are common features of the disease.

Types

Type I (OI) is called osteogenesis imperfect tarda. This disease

Presents in early infancy with fractures secondary to minor trauma and

may be suspected if prenatal ultrasound detects bowing or fractures of

long bones

Type II (OI) osteogenesis imperfect congenita is more severe and batient

The most common mutations cause the substitution of single amino acid

with bulky side chain for the glycine residues

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(References) المصادر

1-WIKIPEDIA

https://en.wikipedia.org/wiki/Main_Page

2-Science Direct

https://www.sciencedirect.com

3-MedlinePlus

https://medlineplus.gov/medlineplus.html

4-Google

https://www.google.com

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أحمد محمود عيد 30104201601066

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