Protein structure & function I

X-ray crystallography

Myoglobin is the first protein to have its 3-dimensional structure revealed by x-ray crystallography

myoglobin binds oxygen in muscles

Structure of Myoglobin

Made up of 153 amino acids

8 helices (A-H)

The ability of myoglobin to bind oxygen depends on the presence of a haem group

It is a globular protein

Porphyrins

The porphyrin ring system is flat

Iron in the ferrous form (Fe2+) lies in the middle of the porphyrin molecule bound to 4 nitrogen atoms

pyrrol

Binding of oxygen to Myoglobin

Types of haem proteins and their functions

Myoglobin (stores oxygen in muscles)

Haemoglobin (Transports oxygen)

Cytochromes (generates energy within the mitochondria)

Function of Haemoglobin

Red blood cells carry oxygen from the lungs to the tissues (high demand). Haemaglobin is the protein which gives blood its red colour and has the role for transporting oxygen around the body

What does haemoglobin consist of

4 chains, 2 identical alpha chains and 2 identical beta chains α2β2

Quaternary structure of haemoglobin

Haemoglobin always has a quaternary structure

The bottom part of the protein structure remains the same but the top part of the protein structure changes with a 15 degree turn

Oxygen binding by myoglobin and haemoglobin

Myoglobin can bind 1 oxygen molecule

Haemoglobin can bind to 4 oxygen molecules

Oxygen binding changes the position of the iron ion

Conformational changes in haemoglobin

Changes of haemoglobin quaternary structure

Deoxyhaemoglobin changes to oxyhaemoglobin