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Lecture 3

Biochemistry 2280A Lecture Notes - Lecture 3: Lysine, N-Terminus, Alanine


Department
Biochemistry
Course Code
BIOCHEM 2280A
Professor
Susan Meakin
Lecture
3

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Topic&#3:&Protein&Structure&
!
!
Learning&objectives:&
1. Distinguish!between!primary,!secondary,!and!tertiary!structure!
2. Describe!the!characteristics!of!an!alpha!helix!and!beta!sheet!
3. Understand!all!the!bonds!and!forces!involved!in!protein!folding!
!
&
Protein&Basics&
!
! Not!all!proteins!share!3D!folding;!some!exist!as!“natively!unstructured!
proteins”(random,!unfolded!conformations)!
! The!function!of!a!protein!depends!on!its!structure!which!depends!on!the!
amino!acid!sequence!
! Are!linear!polymers!of!50J30,000!amino!acids!
!
!
Bonds&and&Reactions&
! The!peptide!bond!is!formed!by!the!carboxyl!group!from!one!amino!acid!
and!the!amino!group!(NH3+)!of!another!
! The!reaction!is!a!condensation!reaction!
! There!are!polarities!on!the!two!opposite!ends!
! Amino!(NJ)!terminal!is!positive;!carboxyl!(CJ)!terminal!is!negative!
! Polypeptides!are!elongated!through!the!CJterminal!
! The!general!pattern!is!NJCJCJNJCJC(!aka!the!backbone)!
! The!peptide!bond!shares!double!bond!characteristics!through!resonance!
between!the!CJO!and!CJN!bonds!!
! Bonds!are!all!covalent!
Does!it!get!
synthesized!
both!sides!or!
just!CJ
terminal?!

Only pages 1-2 are available for preview. Some parts have been intentionally blurred.

! There!is!NO!rotation!around!the!peptide!bond;!this!constrains!its!flexibility!
and!prevents!certain!folding!patterns!
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Primary&structure&
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! Proteins!structures!have!increasing!complexity!from!primary"!secondary"!
tertiary"!quaternary!
! Primary!structure!is!the!sequence!of!residues!that!makes!up!the!protein!
! Only!covalent!bond!is!involved!in!linking!residues!
! Protein!is!usually!~50!residues,!anything!less!are!called!peptides!
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