Summary

Summary The Three-dimensional Structure of Proteins

0 purchase

Course
Molecular And Cell Biology (MCBG2039A)

Institution
University Of The Witwatersrand (wits)

Book
Biochemistry

These notes are a comprehensive summary of chapter 6: The 3-D Structure of Proteins. The topics include: The Secondary Structure: Regular Ways to Fold the Polypeptide Chain. Fibrous Proteins: Structural Materials of Cells and Tissues. Globular Proteins: Tertiary Structure and Functional Diversit...

[Show more]

Preview 3 out of 27 pages

View example

Summarized whole book? No
Which chapters are summarized? Chapter 6
Uploaded on August 3, 2023
Number of pages 27
Written in 2021/2022
Type Summary

molecular and cell biology

R101,00

Add to cart

Add to wishlist

100% satisfaction guarantee
Immediately available after payment
Both online and in PDF
No strings attached

Secondary Structure: Regular Ways to Fold the Polypeptide Chain

Theoretical Descriptions of Regular Polypeptide
Structures
In the early 1950s, Pauling and collaborators
postulated several principles of secondary protein
structures that any such structure must obey:
1. Bond angles and lengths should be like those for
respective free amino acids
2. No atoms should approach one another more
closely than allowed by their van der Waals radii
3. The amide group must remain planar
4. Some kind of noncovalent bonding is necessary to
stabilize a regular folding. Noncovalent bonds
(particularly hydrogen bonds) stabilize folding
processes and products

Steric hindrance can occur due to the overlap of
any atoms in the structure
α-helix β-sheet

𝟑𝟏𝟎 -helix

TJW Notes

,α Helices and β Sheets
• Of the several possible secondary structures for polypeptides, the most frequently observed are the α helix
and the β sheet.
• All of the protein secondary structures shown satisfy the criteria listed earlier.
• In each structure the amide group is planar, and all amide protons and carbonyl oxygens (except a few
near the ends of helices, or edges of sheets) are involved in hydrogen bonding.
• The arrangement of the main-chain hydrogen bonds in the a helix orients the amide N–H and C=O groups
such that the dipole moments for each of these polar bonds align and give rise to a helical dipole moment
(also called a “macrodipole”).
• In effect, the N-terminus of the helix has partial (+) charge character, and the C-terminus has partial (-)
charge character.
α Helix
→ Its center consists of backbone atoms, closely packed together.
→ The hydrogen stabilize the helix and are nearly parallel to the helix axis.
→ Side chains radiate out from helix axis
→ Helix may have distinct hydrophilic and hydrophobic faces

TJW Notes

, β Sheets
→ β sheet: stabilized by inter-chain H bonds; side
chains alternate sides of the sheet
→ A β sheet is composed of two or more β strands
with main-chain hydrogen bonds between adjacent
β strands.
→ There are two ways in which b strands can be
oriented in a β sheet:
⤷ two β strands arranged such that the N-terminus
to C-terminus orientations of the two strands are
in opposite directions ~ antiparallel
⤷ the arrangement with both strands oriented in
the same direction is called ~ parallel
→ In addition to the helices and sheets described
above, there is one more regularly repeating
conformation that is commonly observed in protein
structures—the so-called polyproline II helix.
→ This particular conformation was not predicted on
theoretical grounds because it does not satisfy
Pauling’s requirement for hydrogen bonding.
→ This structure does not have stabilizing hydrogen
bonds between main-chain groups, and it is left-
handed.
→ Roughly a third of the amino acid residues found in
this conformation are prolines, leading to the
designation “polyproline II helix. ”
→ Glycine is also often found in this helix, as are,
albeit to a much lesser extent, several other amino
acids.

TJW Notes

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

You can quickly pay through EFT, credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying this summary from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller tiffanyjanewilton. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy this summary for R101,00. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

69252 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy summaries for 15 years now

Start selling

Summary

Summary The Three-dimensional Structure of Proteins

Document information

Subjects

Connected book

More summaries for

Written for

Seller

Content preview