# Are there proteins with permanently bound magnesium?

Do you know something about the existence of a magnesium containing protein/enzyme in which magnesium is coordinated in the structure and the structure is stable? (like iron in haemoglobin or zinc in zinc fingers)

• Chlorophyll? This is not hard to find :) en.wikipedia.org/w/… – gilleain Jun 12 '17 at 17:23
• @gilleain Chlorophyll isn't a protein. – DavePhD Jun 12 '17 at 17:43
• @DavePhD : Right, I was thinking of the cofactor since OP mentioned haemoglobin but regardless - it's not exactly a rare metal to find in proteins. – gilleain Jun 12 '17 at 20:41

From the look of things you may actually be referring to a lot of different proteins, however I managed to grab two that I found fascinating:

1. Enolase

A glycolytic enzyme which catalyzes the reversible dehydration of 2-phosphoglycerate to phosphoenolpyruvate:

Credits: Lehninger Principles of Biochemistry page 213 ("Enzymes")

• In the enzyme active site, 2-phosphoglycerate undergoes strong ionic interactions with two bound Mg2+ ions causing the resulting intermediate to be easily abstracted.

1. GTPase specifically ARF1 (ARF for ADP-ribosylation factor). These are important in priming phase in the formation of Clathrin-coated vesicles (CCVs).

• Clathrin itself is a protein that forms a polyhedral framework around vesicles that transport TM, GPIlinked, and secreted proteins from the Golgi to the plasma membrane.

X-ray structures of ARF1.GDP and ARF1.GTP, were determined by Dagmar Ringe and by Jonathan Goldberg:

Credits Voet and Voet Biochemistry 4th ed page 435 ("Membrane Assembly and Protein Targeting")

X-ray structures of (a) ARF1.GDP (left) and (b)ARF1.GMPPNP (right) (GMPPNP is a nonhydrolyzable GTP analog in which the O atom linking GTP’s beta- and gamma-phosphorus atoms is replaced by an NH group.)

The bound nucleotides are drawn in stick form in white with their phosphorus atoms magenta and their bound $\ce{Mg^2+}$ ions shown as lavender spheres.

In ARF1.GDP, the protein’s N-terminal helix (red) together with its covalently linked myristoyl group (not present in the X-ray structures) are bound in a shallow hydrophobic groove on the surface of the protein formed in part by the residues of loop gamma 3.

• Thank you for your answer. As far as I am concerned, enolase or other glicolytic enzymes don't have prosthetic groups with magnesium, so the metal in there is just a cofactor, being much of an activator. However, I have never heard about ARF1 and I think that this is the example I'm looking for. Thank you for the hint :) – Cezara Jun 13 '17 at 19:29
• The metal is actually bound to the enzyme enolase :) Read more: Plant Biochemistry J Bonner page 216 > Enolase contains a bound magnesium ion as an essential component... – xavier_fakerat Jun 13 '17 at 19:52
• Anytime! glad I could help :) – xavier_fakerat Jun 13 '17 at 19:58