Symmetry I: Point Symmetry

Question 1

Define Quaternary Structure

Answer 1

The arrangement of multiple protein chains into a multi protein assembly.

Question 2

What are the protein chains of an assembly called?

Answer 2

Subunits.

Question 3

What are three advantages of bringing multiple proteins together?

Answer 3

1. Multiple functions can be brought in close proximity. (Ie. multi-enzyme complexes)
2. (Big containers) Cages of sufficient size can be created. (Ie. Viral capsids)
3. (Large structural components) Long fibers can be obtained. (Ie. microfilaments)

Question 4

There are three ways an object can be considered symmetric. What’s broad detention? And the three ways it can be symmetric?

Answer 4

Broad: an object is said to be symmetric when the object remains the same when you….
1. Rotate it: about a certain access and with a certain angle.
2. Translate it: in a specific direction.
3. Mirror it: with respect to a specific “mirror plane”.
Note: combinations of these operations are possible. Ex. Helical symmetry has both rotational symmetry and translational symmetry.

Question 5

In biomacromolecules no mirror symmetry occurs, why? What does this mean about this course?

Answer 5

Due to the chirality of biomolecules.
This means we will not consider mirror symmetry at all.

Question 6

Define point group symmetry.

Answer 6

Also symmetry axes intersect at one point, the center of the particle.

Question 7

Name the three types of point group symmetry.

Answer 7

Question 8

Name the three types of point group symmetry.

Answer 8

Question 9

In tetrahedral symmetry, what are the folds? How many subunits? (IF there is only 1 subunit type)

Answer 9

Question 10

In octahedral symmetry, what are the folds? How many subunits? (IF there is only 1 subunit type)

Answer 10

Question 11

In Icosahedral symmetry, what are the fold? How many subunits? (IF there is only 1 subunit type)

Answer 11

Question 12

What type of symmetry does GroES have?

Answer 12

C7 point symmetry.

Question 13

What type of symmetry does GroEL have?

Answer 13

D7 Point symmetry.

Question 14

What kind of symmetry does the core of the enzyme: pyruvate dehydrogenase complex have?

Answer 14

Octahedral symmetry (point symmetry).

Question 15

Why do viruses commonly have icosahedral symmetry?

Answer 15

Because viruses have to encapsulate their entire genome inside of their cage. And an efficient way to do that is to encode one protein that conform the very large cage.
Not a lot of genetic material needed to make this protein .

Question 16

If a virus has a icosahedral symmetry capsid (cage) that is made up of 3 different types of proteins, how many total proteins are in the capsid? How do you figure it out?

Answer 16

Icosahedral symmetry makes 60 equivalent subunits. So there are 3 proteins per subunit.
So 3 x 60 = 180 proteins total.