title: Conformation studies of biologically active fragments of bovine growth hormone.
abstract: Conformations of bovine growth hormone active fragments were studied using far ultraviolet circular dichroism and intrinsic fluorescence emission spectroscopy. The small fragment, A-II (segment 96-133 of bovine growth hormone), undergoes a helix to random coil structural transition between pH 5 and 10 (pKa = 7.15). At pH9, the random coil state of A-II reverts back to helix conformation as ionic strength increases from 0.01 to 1. The A-II fluorophore, Tyr-110, is quenched by a neighboring carboxyl group of Glu-111, but is only slightly affected by the secondary structural transition. The large fragment, A-I (segments 1-95 and 134-191, connected via a disulfide linkage, of bovine growth hormone), is a rigidly structured molecule with a large amount of beta-sheet structure. Trp-86 of A-I was found to reside in an aromatic and hydrophobic amino acid cluster which is only destroyed by a high concentration of denaturant. Based on the primary sequence of bovine growth hormone, conformation predictions were made using the Chou-Fasman method ((1974) Biochemistry 13, 222). Bovine growth hormone helical structures are predicted to be in segments 10-34, 66-87, 111-127, and 186-191, beta-Sheet structures are predicted to be in segments 45-54, 90-94, 101-105, 136-142, 161-165, and 174-179. Tetrapeptides 37-40, 41-44, 60-63, 129-132, 146-149, and 156-159 were predicted to be beta turns. The prediction scheme confirmed several spectroscopic observations, but it did not completely explain the behavior of bovine growth hormone peptide fragments.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D013006:Growth Hormone; D009994:Osmolar Concentration; D010446:Peptide Fragments; D011487:Protein Conformation; D011489:Protein Denaturation; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D010446:Peptide Fragments; D013006:Growth Hormone