Protein Modification, targeting and degradation

Protein modification

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Collagen’s unique blend of amino acids

Structure of Collagen

Structure of Collagen (continued)

Structure of Collagen (continued)

An electron micrograph of collagen  from skin

Structure of Collagen (continued)

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Amino acid sequence of collagen

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Osteogenesis imperfecta
 (brittle bone disease)

Proteins can also be cleaved into smaller functional units

How do molecules get in and out of the nucleus?

Protein transport into the nucleus (NLS signal)

Importins and exportins

Improtins and exportins are regulated by Ran

How Ran works

Ran switches between GDP bound and GTP bound

"RanGTP enhances binding between an..."

Ran helps move importins and exportins and their cargo in and out of the nucleus

How HIV controls its own mRNA transport

How do proteins find their way to the endoplasmic reticulum

Then

Protein synthesis on the ER

Protein folding

Chaperones

Protein folding by BiP

Membrane proteins

Further complication of membrane proteins.  Insertion of double pass transmembrane protein with internal signal sequence

Multiple transmembrane sequences are common

Disulfide bonds form between cysteines

Further protein modification

Protein glycosylation

Now in the second step, attachment