Brief Biochemistry of Melittin, a Toxin from Bee Venom

One protein structure that I have been wire modelling quite a bit is melittin, a toxin from honey bee (Apis mellifica) venom (examples below):

Melittin is a 26 amino acid peptide made of two alpha helical sections with a nonpolar N-terminus and a polar C-terminus. This structure resembles a bent rod most likely due to proline-14 causing helix destabilization. Given its structure, it is most often studied as a water-soluble tetramer when isolated at high concentrations in bee venom and a monomer at the lowest concentrations known for cell membrane disruption.

To elucidate, the toxicity of melittin on exposed cells comes from biochemical activities that are hardly mentioned in general discussion. As general knowledge, the most prevalent cause of accidental fatalities from bee venom stings results from allergic reactions in hypersensitive people. However, this lethal reaction is the result of phospholipase A2 and in some cases hyaluronidase. There are a myriad of other toxins in bee venom, such as melittin, that are weakly allergenic, yet still cause biochemical aberrations.

Specifically, melittin has the ability to inhibit some Ca(2+)/calmodulin kinases and ion transport pumps such as NA(+)/K(+) ATPase, thus increasing the cell membrane permeability to ions. In addition, negatively charged membrane lipids are an attractant to melittin, thus favoring melittin incorporation into the membrane leading to cell lysis.

Given the aberrant changes in cell structure from this protein, several complex mechanisms have been observed in bees to prevent autolysis by melittin. This protein is derived from a prepromelittin precursor that underwent a 21-amino acid signal peptide cleavage to form promelittin. Further processing occurs after promelittin is secreted into the bee venom sac to protect the bee from the damaging lytic effects of melittin.



Strong, P. N. & Wadsworth, J. D. F. (2000). Chapter 9:  Pharmacologically Active Peptides and Proteins from Bee Venom. In Rochat, H. & Marie-France Martin-Eauclaire M. (Ed. 1) Animal Toxins: Facts and Protocols. (127-151). Basel Switzerland:  Birkhäuser Verlag.

Terwilliger, T. C. & Eisenberg, D. (1981). “The Structure of Melittin” The Journal of Biological Chemistry, 257(11), 6016-22.

Yang, S. & Carrasquer, G. (1997). “Effect of melittin on ion transport across cell membranes”. Zhongguo Yao Li Xue Bao, 18 (1), 3–5.

New Beginnings: Chemistry and Relationships

I have been wanting to blog again for quite some time now (my last 2 blogs did not last very long, and it has been years since then), but I never found the motivation to sit down and spend a few minutes blogging about my thoughts. To be honest, I think the main contributor to this lack of motivation was my unfailing ability to forget my password. As a side note, I am still locked out of my first blog on Blogspot (now called Blogger) started in 2008. After looking around my room and realizing that my thoughts were strewn on random notebook pages and loose leaf paper, I decided it was time to blog it all out. Therefore, this blog will be dedicated to my random thoughts on science, life, and experimental jewelry designs for my Etsy shop PeachesandScience ( for protein structure jewelry goodies)! If I don’t blog again within the next few months, poke me with a stick. Below is a post I put on Facebook a few weeks ago about the relationship between chemistry and relationships that I have been meaning to blog about but Facebook was the closest thing -.- … Anyway, check it out:

As I was listening to the radio today, I had an “ah-hah!” nerd moment about what chemistry can teach us about some relationships. So the radio host was talking about how a female singer allegedly had an affair with Jay Z a few months ago. Neither him nor his wife Beyonce are causing a scene about this rumor as if nothing ever happened.

That had me thinking lol! Let’s say that the affinity for electrons to bond with other electrons is like a person connecting to another person. Electrons like to be happy, and it is commonplace for electrons to break bonds between atoms to bond to another atom (or atoms) that they are more happy with. When electrons are stressed out or overexcited, the resulting molecule can be quite reactive, such as with reactive oxygen species. These reactive molecules will travel through an organism and take what it needs from other molecules, leaving them damaged with weak or unstable bonds.

If I were to use this analogy for people, I would say that people make and break bonds with others all of the time. Being quick to act reactively and break bonds with others just to create stability within one’s own life may cause more instability and irreversible damage for those others.

I hate to say it, but carbon (an important element in our bodies) is considered a “loose” molecule in the periodic table bonding with whomever it pleases and breaking up when the bond wasn’t good enough. If it didn’t give it up so easy, we wouldn’t be here right now! Holding onto a weak relationship may do more harm than good, even though being “loose” has its own problems lol. That is one of the reasons why silicon-based life wouldn’t work as well here on earth because silicon wants too much stability and i[s] quite reactive when it doesn’t get its way (sounds like my ex-boyfriend…).

It’s not about how many bonds were made or broken, it’s about how strong of a bond it was. If someone you are close to has an affinity towards someone else, it may be because your bond was not as strong as you thought. Think about this:  two nitrogen atoms triple bonded to each other forms one of the strongest bonds in chemistry, according to their bond-dissociation energy (a measurement of bond strength). I like to think of a triple bonded relationship as a bonding of the mind, body and spirit—a bond that reactive people will have a hard time breaking apart.

I am neither Jay Z nor Beyonce so I don’t know anything of their current relationship as a married couple, but their bond appears to be unbroken after this scandal took place—they may be triple bonded. So, if this applies to you or not, I will give this question to ponder: how strong are your bonds with the people in your life?

– August 7, 2013, LM via Facebook

That is all for tonight, till next time, take care!