The solution structure of a monomeric insulin

Abstract

The solution conformation of des-(B26-B30)-insulin (DPI) has been investigated by 'H-NMR spectroscopy. A set of 250 approximate interproton distance restraints, derived from two-dimensional nuclear Overhauser enhancement spectra, were used as the basis of a structure determination using distance geometry (DG) and distance-bound driven dynamics (DDD). Sixteen DG structures were optimized using energy minimization (EM) and submitted to short 5-ps restrained molecular dynamics (RMD) simulations. A further refinement of the DDD structure with the lowest distance errors was done by energy minimization, a prolonged RMD simulation in VUL'UO and a time-averaged RMD simulation. An average structure was obtained from a trajectory generated during 20-ps RMD. The final structure was compared with the des-(B26 -B30)-insulin crystal structure refined by molecular dynamics and the 2-Zn crystal structure of porcine insulin. This comparison shows that the overall structure of des-(B26 -B30)-insulin is retained in solution with respect to the crystal structures with a high flexibility at the N-terminal part of the A chain and at the N-terminal and C-terminal parts of the B chain. In the RMD run a high mobility of Gly A l , Asn A21 and of the side chain of Phe B25 is noticed. One of the conformations adopted by des-(B26-B30)-insulin in solution is similar to that of molecule 1 (Chinese nomenclature) in the crystal structure of porcine insulin.Due to its biological importance as a hormone and drug, insulin has been the subject of numerous studies regarding its structure and function [l]. Several crystal structures of insulins have been reported [2 -61 and a detailed picture of the spatial structure of insulins has emerged.The insulin molecule consists of two polypeptide chains, A and B, of 21 and 30 residues respectively (cf. Fig. 1). The horse-shoe-shaped A chain contains two helices (residues A2-A8 and A13-A20) and the B chain one helix (residues B9 -BI 9). These chains are connected by two disulphide bridges (A7 -B7 and A20 -B19) which, together with a third one (A6 -A1 I), help stabilize the folded form of insulin over a broad range of temperatures and pH values. In the crystal structures the last six residues of the B chain form an antiparallel fl-sheet with another insulin molecule. Insulin is a rather flexible molecule, as evidenced by large structural differences found in different crystal structures. The major differences between various forms of insulin are in the N-terminal of the B chain. For instance, the porcine 4-Zn insulin structure has an additional helical region running from B1 to B8 [4], whereas in 2-Zn insulin this fragment is in a random coil conformation. In fact, a variety of solution and crystal studies showed that the conversion of the 2-Zn to the 4-Zn structure can be induced by high concentrations of anions [7]. Adding Correspondence to R . Boelens, Department of Chemistry, University of Utrecht, Padualaan 8, 3584 CH Utrecht, The NetherlandsAhbveviutions. Des-(3326 -B30)-insulin, insulin lacking the C-te...

Mapping the Functional Surface of Insulin by Design: Structure and Function of a Novel A-Chain Analogue

“…The A-chain N-terminal region is non-helical and imprecisely defined. Motional narrowing in analysis of slowly exchanging amide resonances in 2 H 2 O (Kline & Justice, 1990;Knetgel et al, 1991;Jo rgensen et al, 1992;Hua et al, 1993a,b;Ludvigsen et al, 1994); protection is observed in each case in the B-chain a-helix and C-terminal A-chain helix. DKP-[A6-A11] Ser exhibits novel non-native features.…”

“…This view is supported by three additional observations. First, of native elements of secondary structure, only the A1-A8 a-helix fails to exhibit protection of amide protons from exchange (Kline & Justice, 1990;Hua et al, 1991Knetgel et al, 1991;Jo rgensen et al, 1992;Ludvigsen et al, 1994). Second, among crystal structures the A1-A8 helix is least regular in geometry and most readily deformed by lattice packing (Badger, 1992).…”

Structural modifications of oxidized insulin B-chain induced by glycerol addition

“…The B-chain secondary structure in the native insulin consists of an N-terminal region of variable conformation (residues B1-B8), a central a-helix between two disulfide bridges (B9-B19), a [3-turn (B20-B23) and a C-terminal [3-strand (B24-B28) [13,14,16].…”

“…Indeed, several groups have published NMR study results, carried out at low pH using modified insulins or co-solvents, in an effort to counteract its selfassociation behavior [12][13][14][15][16]. This study has been carried out by 2D-1H-NMR and CD spectroscopies.…”

Insulin & Related Proteins - Structure to Function and Pharmacology

“…The functional surface of insulin has long been the object of speculation Pullen et al, 1976; Despite many years of investigation by mutagenesis (Katsoyannis et al, 1973;Cosmatos and Katsoyannis, 1975;Danho et al, 1975;Inouye et al, 1978;Tager et al, 1979;Inouye et al, 1981;Kobayashi et al, 1982;Okada et al, 1981;Shoelson et al, 1983;Kitagawa et al, 1984;Kobayashi et al, 1986;Nakagawa and Tager, 1986;Nanjo et al, 1986;Nakagawa and Tager, 1987;Casaretto et al, 1987;Mirmira and Tager, 1989;Wang et al, 1991;Mirmira and Tager, 1991;Nakagawa and Tager, 1992;Hu et al, 1993;Kaarsholm et al, 1993;Weiss et al, 2000), nuclear magnetic resonance (NMR) 1 spectroscopy (Hua and Weiss, 1990;Knegtel et al, 1991;Hua et al, 1992;Sørensen and Led, 1994;Hua et al, 1995;Jørgensen et al, 1996;Hua et al, 1996;Olsen et al, 1996;Ludvigsen et al, 1998;Olsen et al, 1998;Kurapkat et al, 1999) 103 and X-ray crystallography Peking Insulin Structure Group, 1971;Bi et al, 1984;Liang et al, 1985;Dai et al, 1987;Badger et al, 1991;Derewenda et al, 1991...…”