Positive (+)
and
Negative (-)
charges on the surface of a protein molecule play crucial roles in its interactions with other molecules, and hence in its functions.
Electrostatic potential maps coloring the surface of a protein molecule are a popular way to visualize the distribution
of surface charges. Easy to use free software is available to to create these surface maps.
Above is an integral membrane potassium channel protein. One of its 4 identical chains is removed so you can see the Negative (-)
protein surface contacting the
3 K+ ions.