The rule states that the N-terminal amino acid of a protein determines its half-life (time after which half of the total amount of a given polypeptide is degraded).
[5] Proteins bearing an N-terminal Primary destabilising residue are specifically recognised by the bacterial N-recognin (recognition component) ClpS.
[10] The first piece of evidence comes from the endosymbiotic theory which encompasses the idea that chloroplasts are derived from cyanobacteria, photosynthetic organisms that can convert light into energy.
[7] This study suggests that ClpS1 is functionally similar to ClpS, also playing a role in substrate recognition via specific N-terminal residues (degrons) like its bacterial counterpart.
[15] It is posited that upon recognition, ClpS1 binds to these substrate proteins and brings them to the ClpC chaperone of the protease core machinery to initiate degradation.
[15] In another study, Arabidopsis thaliana stromal proteins were analyzed to determine the relative abundance of specific N-terminal residues.
[20][21] In vitro data demonstrate that Plasmodium falciparum ClpS is able to recognize a variety of N-terminal primary destabilizing residues, not only the classic bacterial Primary destabilizing residues (leucine, phenylalanine, tyrosine and tryptophan) but also N-terminal Isoleucine and hence exhibits broad specificity (in comparison to its bacterial counterpart).