C4 S2con&S3

1° prim AAS combined by

covalent bonds

2° ndary Struc

• α helix

• β pleated sheet & turns

held together by h-bonds in relative locations

3° ter struc

“long range“ H bonds, ionic, S-S

4° quart Struc

2 or more polypep chains 

2 major groups of proteins

Fibrous

Globular

Fibrous Proteins 3

• provide protection, strength, and/or flexibility

• polypep chains are arranged in long strands or sheets

• fundamental structural units are simple repeating elements of 2ndary struc

  • water - insol. (non-P aas)

ex of Fibrous proteins

Collagens - most abundant, major in connective tissue

Elastin - found in some connect. tiss. wall of artery, lung, intest.

Keratin:

• alpha - hair, nails, outer layer of skin 

  • beta - skin of reptiles and birds

Globular proteins 4

• have dynamic func. (cataly, and transp)

• polypep chain folded into spherical or globular shape. Often contain several types of 2nd struc

  • Water soluble (polar & charged) 

most proteins fall into this category

In Globular proteins, what affinities are in the inside vs the outside of the protein?

non-polar on the inside

polar & ionizable groups are in the outside

ex of globular proteins 5

• myoglobin

• hemoglobin

• ferritin

• most enzymes (krebb)

• transferin

collagen (def)

found in connective tissue such as cartilage, tendons, organic matrix of the bone and the cornea of the eye

collagen (info) 4

• most abundant protein in mammals

• 3 alpha-chains are super-twisted into the collagen triple helix

• alpha chains contain G-X-Y repeats:

  • G = Glycine

  • X = Pro

  • Y = HyPro

• Triple helix has higher tensile strength than a steel wire of equal cross section

in collagen, Pro does what?

pro & hypro? permit sharp turns

in collagen, Gly does what

is good in tight spots b/c it is small & flexible

the hydroxyl group in 4-hydroxyproline in collagen 2

• forces the proline ring into a favorable pucker → bending

• provides opportunity for more hydrogen bonding b/t 3 collagen strands

3° tert Struc 3

• refers to overall spatial arrangement of atoms in a protein

• stabilized by numerous weak interactions b/t amino acid side chains

  • largely hydrophobic and polar interactions

  • ion-ion ints. disulph bonds contribute to stability

• interacting aas are often not near each other in the 1prim sequ

5 interactions that stabilize 3 and 4 protein structures

1. hydrogen bonding

2. hydrophobic int

3. ion-ion int

4. disulfide bridge

5. van der whaal?

Interactions describe them

1°

2°

3°

4°

1° = amide band joining two aas

2° = h bonds made from backbone

3° = anything connected w/ r-grps

4° = connect 2 diff. pept chains

Globular protein (in depth)

• different segments of polypep chain fold back on one another generating a more compact shape than in fibrous proteins

• d/c of this folding, there is a much greater structural diversity in globular proteins

  • more kinds of 2° structures

  • greater struc diversity = b/c greater func diversity
    
    myoglobin was the first globular protein studied in detail

4° Quart in depth

• refers to 3° D stuc of multimeric proteins (interactions b/t subunits)

  • structures are a result of specific interactions b/t subunits of the multimeric process

    • these ints. are the same 4 types of ints that maintain 3° struc