I’m sure the explanation of vaccines has been given to the reader many times. The whole process of vaccine administration is an artificial manipulation of the human adaptive immune system. This part of our immune system can react and develop an immunological memory to counteract specific microbes. The other part of our immune system is the innate immune system. The innate immune system is found in some form across all animals and plants. Skin can be seen as the first level of defence but other non physical protection also counts. Inflammation that increases blood flow and brings other cells which trigger the adaptive immune system is another example. But the aspect which is important for today’s post is that of antimicrobial peptides.
Luckily the prokaryotic cells of microbes are different in key ways to the eukaryotic cells of animals and these differences are prime targets for peptides to attack. Cell wall production, DNA replication and protein folding are all features which cripple a bacterium if prevented. Normally these peptides hunt down the bacteria by attracting to the negative charge on most bacterial surfaces. Once attached they either integrate into the membrane or even sometimes break through to mess up the intracellular chemicals of the microbe.
Over the last twenty years more and more bioactive peptides have been found and linked to certain protein sequences in the body. But none of these were specifically searched for, merely located by chance in other research. Recent work has aimed to improve on this by actively looking for antimicrobial peptides as part of proteins. Of course a protein consists of many polypeptides which themselves consist of many peptides. Trial and error will not get you very far when looking for a particular characteristic. The method employed is the logic that it is the chemical nature of the peptides and polypeptides which then translate into a particular structure of the protein. Researchers used a program they designed, called Kamal, which looked through long protein chains for certain physiochemcial traits which could imply that an antibacterial peptide is present. These traits are those such as charge and hydrophobicity and whenever a successful antimicrobial is found, its traits can be re-entered back into Kamal to be searched for in the next filtering round. Yet a finding based on characteristics does not mean you understand why something happens. More research needs to be done to understand exactly how these peptides work chemically and how these qualities translate into their encrypted polypeptide structure.
Paper links: Encrypted Antimicrobial Peptides from Plant Proteins