JAK-STAT transducer mechanism is seen i

(Growth hormone) (50-KDT6th)JAK-STAT- Kinase binding receptors - These receptors differ in not having any intrinsic catalytic domain.Agonist induced dimerization alters the intra cellular domain. Conformation to increase its affinity for a cytosolic tyrosine protein kinase JAK. On binding. JAK gets activated and phosphorylates tyrosine residues of the receptors which now binds another free moving protein ST AT (signal transducer and activator of transcription) which is also phosphorylated by JAK pairs of phosphorylated ST AT dimerize and translocate to the nucleus to regulate gene trans cription resulting in a biological responseMany cytokines, growth hormone, interferons etc act through this type of receptorSpare receptors are exhibited by insulin receptorsTransducer Mechanisms 1. G- protein coupled receptors2. Receptors with intrinsic ion channel 3. Enzyme linked receptorsa. Intrinsic enzyme receptors b. JAK-STAT- kinase- binding receptors4. Receptors regulating gene expression (Transcription factors)SPARE-RECEPTORS - one agonist receptor binding event can lead to the activation of many more cellular response elements. Thus only a small fraction of the total receptors need to be bound to elicit a maximum- cellular response