Fragments of functional proteins: Role in endocrine regulation

Systematic analysis of structures, localization, formation and biological a ctivities of endogenous peptides derived from functional proteins, such as hemoglobin, myelin basic protein, immunoglobulins, etc., allowed establishi ng the basic features of that group of compounds. The sets of these peptide s in mammalian tissues, or "tissue-specific peptide pools" are: (i) tissue specific; (ii) stable at normal conditions; (iii) conservative in the same tissues of different mammalian species; (iv) dependent on the general state of homeostasis of tissue or the whole organism. Formation of such peptides has features of both conformation and site specificity and also involves t he action of carboxy- and amino-peptidases. As a result, the families of st ructurally related families of peptides are generated. The fragments of fun ctional proteins exhibit a wide range of the biological effects, characteri stic both for hormones and parahormones, from hormone-releasing to growth-r egulatory activity. At the same time, the molecular mechanisms of action of the majority of such peptides are unknown. On the basis of the data obtain ed the components of tissue-specific peptide pools are considered to form a novel regulatory system, complementary to other peptidergic systems such a s hormonal, nervous, immune, etc. The biological role of the fragments of f unctional proteins in vivo and the patterns of interaction with other regul atory systems are suggested.