ABSTRACT
This chapter presents an overview of the role of proteins as biological effectors. Proteins as biological effectors, as distinct from structural proteins, such as collagen and keratin, can be divided into six major groups: enzymes, regulatory proteins, receptors, immune proteins, carrier proteins, and contractile proteins. The chapter examines the impact of structural conservation and variation on protein's ability to function as a biological selector and effector. It also examines the salient features of proteins of the blood coagulation or clotting pathway and the immunoglobulin-activated complement pathway to illustrate how protein systems can identify threats to the homeostasis of organism. The chapter analyses some effector features of the gonadotropins, a family of endocrine glycoprotein hormones secreted by the pituitary gland and which must reach their target cells in ovary and testis via the circulatory system. It discusses the structure and biochemical mechanisms of growth factor action to highlight the diversity of transduction of effector signals into intracellular compartments by membrane receptors.
