Enhancing the activity of insulin at receptor edge: crystal structure and photo-cross-linking of A8 analogues
[INS_HUMAN] Defects in INS are the cause of familial hyperproinsulinemia (FHPRI) [MIM:176730].    Defects in INS are a cause of diabetes mellitus insulin-dependent type 2 (IDDM2) [MIM:125852]. IDDM2 is a multifactorial disorder of glucose homeostasis that is characterized by susceptibility to ketoacidosis in the absence of insulin therapy. Clinical fetaures are polydipsia, polyphagia and polyuria which result from hyperglycemia-induced osmotic diuresis and secondary thirst. These derangements result in long-term complications that affect the eyes, kidneys, nerves, and blood vessels. Defects in INS are a cause of diabetes mellitus permanent neonatal (PNDM) [MIM:606176]. PNDM is a rare form of diabetes distinct from childhood-onset autoimmune diabetes mellitus type 1. It is characterized by insulin-requiring hyperglycemia that is diagnosed within the first months of life. Permanent neonatal diabetes requires lifelong therapy.  Defects in INS are a cause of maturity-onset diabetes of the young type 10 (MODY10) [MIM:613370]. MODY10 is a form of diabetes that is characterized by an autosomal dominant mode of inheritance, onset in childhood or early adulthood (usually before 25 years of age), a primary defect in insulin secretion and frequent insulin-independence at the beginning of the disease.  
[INS_HUMAN] Insulin decreases blood glucose concentration. It increases cell permeability to monosaccharides, amino acids and fatty acids. It accelerates glycolysis, the pentose phosphate cycle, and glycogen synthesis in liver.
Publication Abstract from PubMed
The receptor-binding surface of insulin is broadly conserved, reflecting its evolutionary optimization. Neighboring positions nevertheless offer an opportunity to enhance activity, through either transmitted structural changes or introduction of novel contacts. Nonconserved residue A8 is of particular interest as Thr(A8) --> His substitution (a species variant in birds and fish) augments the potency of human insulin. Diverse A8 substitutions are well tolerated, suggesting that the hormone-receptor interface is not tightly packed at this site. To resolve whether enhanced activity is directly or indirectly mediated by the variant A8 side chain, we have determined the crystal structure of His(A8)-insulin and investigated the photo-cross-linking properties of an A8 analogue containing p-azidophenylalanine. The structure, characterized as a T(3)R(3)(f) zinc hexamer at 1.8 A resolution, is essentially identical to that of native insulin. The photoactivatable analogue exhibits efficient cross-linking to the insulin receptor. The site of cross-linking lies within a 14 kDa C-terminal domain of the alpha-subunit. This contact, to our knowledge the first to be demonstrated from the A chain, is inconsistent with a recent model of the hormone-receptor complex derived from electron microscopy. Optimizing the binding interaction of a nonconserved side chain on the surface of insulin may thus enhance its activity.
Enhancing the activity of insulin at the receptor interface: crystal structure and photo-cross-linking of A8 analogues.,Wan Z, Xu B, Huang K, Chu YC, Li B, Nakagawa SH, Qu Y, Hu SQ, Katsoyannis PG, Weiss MA Biochemistry. 2004 Dec 28;43(51):16119-33. PMID:15610006
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.