In this lecture, we will build on the knowledge gained from lecture 5 to look into the structure and function of proteins.

We will talk about different ways to look at protein structures and how to classify them. We will start by focusing on the fibrous protein structures that make up all the large structural building blocks in our bodies, and how they even reach macroscopic scales by a hierarchy of structures (do you see how the concept of using building blocks on many levels keeps recurring?)

We will look at things like silk, collagen, teeth, hair, and the coiled-coil helices that are common in muscle fibers. This in turn will cause us to look more at helix packing to understand why these coiled coils are so common.

After this, we will look at the globular proteins, i.e. normal water-soluble ones. These exhibit a huge diversity of structure that both provides wonderful illustrations to the things we have peeked at in previous lectures, and an historical overview of how we have learnt about proteins. We will study their topology, 3d-organization, and also look at the correspondence between genes, introns/exons, and structure. Finally we will look at some ideas how this can be used to engineer proteins, which we'll come back to towards the end of the class.

Lecture recording

Playlist of all lecture 7 concepts

Isolated concepts:

Slides with still images from videos

(Some students found these useful to take notes)

Full-format stills

Handout-format stills

Reading suggestions

Finkelstein, chapters 11, 13, 14

Study questions

What are the conceptual differences between fibrous, globular and membrane proteins?
Why are water-soluble proteins called “globular”?
Name a couple of fibrous proteins - where do they occur?
Where does silk gets it properties from?
Why are fibrous proteins always created from simple repeating units?
Why do most fibrous proteins contain links like disulfides or h-bonds between chains?
What is leucine zipper?
What is the normal number of residues per turn in an alpha helix?
Why is the number of residues/turn sometimes slightly different in coiled-coils?
Test yourself: Based on the pitch distance in a helix, and that hair grows maybe 0.5mm/day, roughly how many turns are added to each alpha helix per second?
What happens when a hairdresser creates a permanent?
What is “TMV”? What are the constituent building blocks of it?
What is “supersecondary structure”?
What is a Rossman fold? What is a Greek key?
How do β sheets influence dimerization?
What do we mean by a “fold”? Roughly how many are there? Is the number surprisingly small or large? Why?
Which class of proteins has largest diversity?
What is the difference between α/β proteins and α+β proteins?
How can you use e.g. hydrophobic moment design of helices/sheets in protein engineering in modern biotechnology?
What are the roles of introns vs. exons in genes? How do they relate to structure of proteins?

Other reading