Relationship Between Structures And Functions Of Prothoracicostatic Peptide And Its Analog Peptides

Relationship Between Structures and Functions of Prothoracicostatic Peptide and its Analog PeptidesInsect brain neuropeptides are the important regulatory hormones (or factors) generated in brain, which control the activities of many organs (or glands) and important physiological events in insects, for instance, growth, development, ecdysteroidogenesis, metamorphosis, behavior, metabolism, generation, inheritance and so on. Research on the insect brain neuropeptides and neuroendocrine system is one of the important fields of modem molecular biology, and is also a frontier field of beneficial insect utilization and biological pesticides development. It is crucial to deeply understand the biological phenomenon and the rules of insect life activities, and to study the structure characteristics and the relationship between the structures and functions of insect neuropeptide, which has, moreover, very significant value in basic science and practice meanings to provide new way of pest management and cure for people.Bombyx mori prothoracicostatic peptide (Bom-PTSP) is a novel bisect neuropeptide, which was isolated from the larval brains of the silkworm, Bombyx mori, and identified by Hua et al. in 1999. The primary structure is AWQDLNSAW-NH2 and molecular mass 1089.78D. The main function of Bom-PTSP is that it inhibits ecdysteroidogenesis when prothoracic gland (PG) of the silkworm was active, and when PG is not active, prothoracicotropic hormone (PTTH) activate PG, whereas Bom-PTSP almost completely inhibits PTTH-stimulated ecdysteroidogenesis when PG was incubated in medium of PTTH and Bom-PTSP combination in vitro. PTSP cooperates with PTTH to regulate and control ecdysteroidogenesis on prothoracic gland of insect. Ecdysteroid is one of important hormones of growth, development, ecdysteroidogenesis and metamorphosis of insect; thus, PTSP also plays an important role in insect metamorphosis. Techniques of culture of prothoracic gland (PG) in vitro, 3H-ecdysteroid-Radiounniunoassay, and methods of molecular biology and biophysics, for instance, nuclear magnetic resonance (NMR), circular dichroism CD) and so on were engaged. The biological activity on ecdysteroidogenesis in vitro and in vivo of a group of analog peptidesof Bom-PTSP synthesized by chemical modifications and the relationship between the structures and functions were studied. In order to further research the relationship between structure and function of Bom-PTSP, part cDNA sequence of PTSP of cotton bollworm, Heliocoverpa ormigera was also studied.1. Biological activities of analog peptides of Bombyx mori prothoracicostaticpeptide and the relationship with their structuresBased on the amino acid sequence of Bom-PTSP, AWQDLNSAW, a group of analog peptides of Bom-PTSP was synthesized by chemical modifications, such as adding, removing, replacing amino acid of the peptide. Dissecting the prothoracic glands, by using silkworms' prothoracic glands in vitro culture and H-ecdysteroid-radioimmunoassay, the biological activities of those analog peptides were examined, and their active features, chemical parameters, as well as the relationship between structures and functions of those peptides were analyzed and compared. With an exception of 899808 having the sequence of AWQDLSAW that affected like Bom-PTSP, 899805 (AWQDLNS) and 899809 (AWQDLNSGAW) partially stimulated ecdysteroidogenesis in a dose dependent manner, whereas 899803 (DLNSAW), 899804 (AWQDLNSA), 899806 (AWQDLN) as well as 899807 (AWQDLNSAWA) had both stimulatory and inhibitory effects on ecdysteroidogenesis, depending on the concentrations. In principle, any change at the amino acid sequence or length of Bom-PTSP results in decrease, loss or contrary of its inhibitory activity on ecdysteroidogenesis.2. In vivo activity of prothoracicostatic peptide in the silkworm, Bombyx moriFor the sake of further research on the function of PTSP to ecdysteroidogenesis in vivo, based on the culture experiments in vitro, prothoracicostatic peptide was injected into the B. mori hemolym...