Sbw 03 Proteins

8/12/2019 Sbw 03 Proteins

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PROTEINS

FOLDED POLYPEPTIDES

2007 Paul Billiet ODWS
http://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.html


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PRIMARY STRUCTURE

The sequence of amino acids

MIL1 sequence:>gi|7662506|ref|NP_056182.1| MIL1 protein [Homo sapiens]

MEDCLAHLGEKVSQELKEPLHKALQMLLSQPVTYQAFRECTLETTVHASGWNKILVPLVLLRQMLLELTRLGQEPLSALLQFGVTYLEDYSAEYIIQQGGWGTVFSLESEEEEYPGITAEDSNDIYILPSDNSGQVSPPESPTVTTSWQSESLPVSLSASQSWHTESLPVSLGPESWQQIAMDPEEVKSLDSNGAGEKSENNSSNSDIVHVEKEEVPEGMEEAAVASVVLPARELQEALPEAPAPLLPHITATSLLGTREPDTEVITVEKSSPATSLFVELDEEEVKAATTEPTEVEEVVPALEPTETLLSEKEINAREESLVEELSPASEKKPVPPSEGKSRLSPAGEMKPMPLSEGKSILLFGGAAAVAILAVAIGVALALRKK

length: 386amino acids Anne-Marie Ternes
http://kachkeis.com/essay2.htmlhttp://kachkeis.com/essay2.htmlhttp://kachkeis.com/essay2.htmlhttp://kachkeis.com/essay2.htmlhttp://kachkeis.com/essay2.htmlhttp://kachkeis.com/essay2.html


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PRIMARY STRUCTURE The numbers of amino acids vary

(e.g. insulin 51, lysozyme 129, haemoglobin574, gamma globulin 1250)

The primary structure determines the folding of

the polypeptide to give a functional protein Polar amino acids (acidic, basic and neutral)

are hydrophilic and tend to be placed on theoutside of the protein.

Non-polar (hydrophobic) amino acids tend to beplaced on the inside of the protein



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Infinite variety

The number of possible sequences isinfinite

An average protein has 300 amino acids,At each position there could be one of 20different amino acids= 10390 possible combinations

Most are uselessNatural selection picks out the best



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SECONDARY STRUCTURE

The folding of the N-C-

C backbone of the

polypeptide chainusing weak hydrogen

bonds

Science Student

Text 2007 Paul Billiet ODWS
http://science-student.com/course-notes/biology-notes/biology-proteinshttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://science-student.com/course-notes/biology-notes/biology-proteins


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SECONDARY STRUCTURE

This produces the alpha helix and beta pleating

The length of the helix or pleat is determined by certainamino acids that will not participate in these structures

(e.g. proline)

Dr Gary Kaiser Text2007 Paul Billiet ODWS
http://student.ccbcmd.edu/~gkaiser/biotutorials/proteins/fg4b.htmlhttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://student.ccbcmd.edu/~gkaiser/biotutorials/proteins/fg4b.htmlhttp://student.ccbcmd.edu/~gkaiser/biotutorials/proteins/fg4b.html


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TERTIARY STRUCTUREThe folding of the polypeptide into

domains whose chemical properties are

determined by the amino acids in the

chain

MIL1 protein

Anne-Marie Ternes

http://kachkeis.com/essay2.htmlhttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://kachkeis.com/essay2.htmlhttp://kachkeis.com/essay2.htmlhttp://kachkeis.com/essay2.htmlhttp://kachkeis.com/essay2.htmlhttp://kachkeis.com/essay2.html


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TERTIARY STRUCTURE

This folding is sometimes held together bystrong covalent bonds(e.g. cysteine-cysteine disulphide bridge)

Bending of the chain takes place at certainamino acids(e.g. proline)

Hydrophobic amino acids tend to arrange

themselves inside the molecule Hydrophilic amino acids arrange themselves

on the outside



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Max Planck Institute for Molecular Genetics

Chain B of Protein Kinase C
http://lectures.molgen.mpg.de/ProteinStructure/Levels/index.htmlhttp://lectures.molgen.mpg.de/ProteinStructure/Levels/index.html


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QUATERNARY STRUCTURE

Some proteins are

made of several

polypeptide subunits(e.g. haemoglobin has

four)

Protein Kinase C

Max Planck Institute for Molecular Genetics

Text 2007 Paul Billiet ODWS
http://lectures.molgen.mpg.de/ProteinStructure/Levels/index.htmlhttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://lectures.molgen.mpg.de/ProteinStructure/Levels/index.html


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QUATERNARY STRUCTURE

These subunits fit together to form the

functional protein

Therefore, the sequence of the aminoacids in the primary structure will influence

the protein's structure at two, three or

more levels



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Result

Protein structure depends upon the

amino acid sequence

This, in turn, depends upon the sequenceof bases in the gene



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PROTEIN FUNCTIONS

Protein structure determines protein

function

Denaturation or inhibition which maychange protein structure will change its

function

Coenzymes and cofactors in general mayenhance the protein's structure



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Fibrous proteins

Involved in structure: tendons ligaments

blood clots

(e.g. collagen and keratin) Contractile proteins in movement: muscle,

microtubules

(cytoskelton, mitotic spindle, cilia, flagella)



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Globular proteins

most proteins which move around (e.g.

albumen, casein in milk)

Proteins with binding sites:enzymes, haemoglobin, immunoglobulins,

membrane receptor sites



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Proteins classified by function CATALYTIC: enzymes

STORAGE: ovalbumen (in eggs), casein (in milk), zein(in maize)

TRANSPORT: haemoglobin

COMMUNICATION: hormones (eg insulin) andneurotransmitters

CONTRACTILE: actin, myosin, dynein (in microtubules)

PROTECTIVE: Immunoglobulin, fibrinogen, blood

clotting factors TOXINS: snake venom

STRUCTURAL: cell membrane proteins, keratin (hair),collagen


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Sbw 03 Proteins