Submitted to: European Journal of Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/1999
Publication Date: N/A
Interpretive Summary: Because of problems with the development of resistance to conventional pesticides, there is a critical need for new concepts and alternative approaches in controlling such pests. The basic premise of this research is that peptides (short chains of amino acids) serve as potent internal messengers in insects to regulate vital functions. Peptides themselves are unsuitable for control measures due to their instability to enzymes in the circulatory and digestive systems of the insect. New, selective control measures may be developed by designing metabolically stable mimics of these neuropeptides that actively inhibit or over-stimulate functions regulated by them, resulting in disruption of the internal environment of the insect. One of the important pieces of information required to develop neuropeptide-based pest control strategies is to identify the different structural forms that members of the sulfakinin neuropeptide family have within the internal environment of insects and their impact on the function and potency of action of these regulatory molecules. This work leads us one step closer to the development of practical neuropeptide-like chemicals that will be effective in controlling certain pest insects in an environmentally friendly fashion.
Technical Abstract: We identified and chemically characterized the two major forms of sulfakinins from an extract of 800 corpora cardiaca/corpora allata complexes of the American cockroach, Periplaneta amencana. Bioactivity during the purification was monitored by measuring heart beat frequency in a preparation in situ. By Edman degradation analysis and MS, these main forms were identified as having the primary structures Pea-SK [EQFDDY(S03H)GHMRFamide] and Lem-SK-2 [pQSDDY(SO3H)GHMRFamide]. The sulfation was confirmed by UV, MS and peptide synthesis. In addition, post-translationally modified sulfakinins of both major forms were isolated and identified. Firstly, nonsulfated forms of these peptides are present in considerable amounts in the corpora cardiaca/allata. Secondly, the N-terminally blocked Pea-SK and the nonblocked Lem-SK-2 occur naturally in neurohaemal release sites. Thirdly, modified Pea-SK with 0-methylated glutamic acid occurs which is not an artifact of peptide purification. The major forms of the sulfakinins were shown to be highly active on both the heart and hindgut with threshold concentrations of about 5 x 10-10 M (heart) and 2 x 1O-9 M (hindgut).