S-100 Protein in Clonal Astroglioma Cells Is Released by Adrenocorticotropic Hormone and Corticotropin-Like Intermediate-Lobe Peptide

S-100 protein in clonal GA-1 and C6 rat glioma cell lines was released in serum-free medium supplemented with adrenocorticotropic hormone (ACTH). The induction of S-100 protein release by ACTH was dose-dependent, showing a half-maximal release at about 5 microM, and the S-100 protein concentration in the medium increased sharply within 3 min, but slightly during further incubation. The S-100 protein release was apparently accompanied by a decrease in the membrane-bound form of S-100 protein in the cell. The S-100 protein release was induced not by the ACTH1-24 fragment, which exhibits the known effects of ACTH, but by the ACTH18-39 fragment, which is designated as corticotropin-like intermediate-lobe peptide (CLIP). These results indicate that the C-terminal half of ACTH is responsible for the S-100 protein release. The enhancement of S-100 protein release by ACTH was also observed in normal rat glioblasts. The release induced by ACTH was apparently specific to S-100 protein, because little release of the cytoplasmic enzymes, creatine kinase, and enolase was observed under the same conditions. High concentrations (5 mM) of dibutyryl cyclic AMP or dibutyryl cyclic GMP were also found to induce S-100 protein release; however, catecholamines (epinephrine, norepinephrine, isoproterenol, and dopamine), acetylcholine, and glutamic acid did not enhance the release.(ABSTRACT TRUNCATED AT 250 WORDS)     

pH dependence of individual tryptophan N-1 hydrogen exchange rates in lysozyme and its chemically modified derivatives

Nuclear magnetic resonance analyses have been made of the individual hydrogen-deuterium exchange rates of tryptophan indole N-1 hydrogens in native lysozyme and its chemically modified derivatives including lysozyme with an ester cross-linkage between Glu-35 and Trp-108, lysozyme with an internal amide cross-linking between the epsilon-amino group of Lys-13 and the alpha-carboxyl group of Leu-129, and lysozyme with the beta-aspartyl sequence at Asp-101. The pH dependence curves of the exchange rates for Trp-63 and Trp-108 are different from those expected for tryptophan. The pH dependence curve for Trp-108 exchange exhibits the effects from molecular aggregation at pH above 5 and from a transition between the two conformational fluctuations at around pH 4. The exchange rates for tryptophan residues in native lysozyme and modified derivatives are not correlated with the thermodynamic or kinetic parameters in protein denaturation, suggesting that the fluctuations responsible for the exchange are not global ones. The exchange rates for tryptophan residues remote from the modification site are perturbed. Such tryptophan residues are found to be involved in a small but distinct conformational change due to the modification. Therefore, the perturbations of the N-1 hydrogen exchange rates are related to the minor change in local conformation or in conformational strain induced by the chemical modification.     

Effect of histamine H1-receptor antagonist on the regulation of carbohydrate and lipid metabolism in rat liver

In order to elucidate the role of histamine in the liver, we studied the effect of a histamine H1-receptor antagonist on the carbohydrate and lipid metabolism in the rat liver. The administration of the H1-receptor antagonist decreased significantly the contents of glycogen and malonyl-CoA in the liver. However, it did not affect the levels of serum glucose and free fatty acid. These results suggest that histamine may play a part in the regulation of metabolism of carbohydrates and lipids in the liver.     

Potassium channels from NG108-15 neuroblastoma-glioma hybrid cells. Primary structure and functional expression from cDNAs

The complete amino acid sequences of two potassium channel proteins from NG108-15 neuroblastoma-glioma hybrid cells have been deduced by cloning and sequencing the cDNAs. One of these proteins (NGK2) is structurally more closely related to the Drosophila Shaw gene product than to the Shaker and Shab gene products, whereas the other (NGK1) is identical with a rat brain potassium channel protein (BK2) which is more closely related to the Drosophila Shaker gene product. mRNAs derived from both the cloned cDNAs, when injected into Xenopus oocytes, direct the formation of functional potassium channels with properties of delayed rectifiers.     

Immunohistochemical localization of plasma retinolbinding protein and prealbumin in human pancreatic islets

Summary This study was undertaken, employing the immunoenzyme method, to confirm the presence of retinol-binding protein in human pancreatic islets, and to compare its distribution with that of prealbumin, insulin, glucagon, somatostatin and pancreatic polypeptide. It was found that most islet cells contained retinol-binding protein, although centrally located cells showed stronger reactivity than those in the peripheral region. The distribution of each of the five polypeptides differed from that of retinolbinding protein, indicating that these peptides did not cross-react with anti-retinol-binding protein antibody. Islet cells which contained prealbumin, on the other hand, were mostly classified as A cells. Further studies are necessary to confirm whether the islet cells produce retinol-binding protein or only store it.     

Unfolding rates of globular proteins determined by kinetics of proteolysis

A convenient method for the determination of unfolding rates of small globular proteins under physiological conditions was developed using digestion with proteases. The apparent first-order rate constants for digestion of lysozyme with thermolysin and with Pronase at pH 8 and 50 degrees C were shown to be saturated with increases of concentrations of these proteases. The maximum rate constants extrapolated were identical in digestions with two different proteases, and were found to be equal to the unfolding rate constant of lysozyme. Similarly, the unfolding rate constant of RNase A at pH 8 and 50 degrees C, and those of lysozyme, RNase A and beta-lactoglobulin at pH 8 and 40 degrees C, were determined by the digestion method. Thus, it was shown that digestion by proteases proceeds mainly via the unfolded state of proteins.     

Isolation and characterization of 101-beta-lysozyme that possesses the beta-aspartyl sequence at aspartic acid-101

In the reaction of the intramolecular cross-linking between Lys-13 (epsilon-NH3+) and Leu-129 (alpha-COO-) in lysozyme using imidazole and 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride [Yamada, H., Kuroki, R., Hirata, M., & Imoto, T. (1983) Biochemistry 22, 4551-4556], it was found that two-thirds of the protein (both the recovered and cross-linked lysozymes) showed a lower affinity than the rest against chitin-coated Celite, an affinity adsorbent for lysozyme. The protein with the reduced affinity was separated on chitin-coated Celite affinity chromatography and found to be slightly different from native lysozyme in the elution position of the tryptic peptide of Ile-98-Arg-112 on reversed-phase high-performance liquid chromatography. In contrast with native lysozyme, the limited hydrolysis of this abnormal tryptic peptide of Ile-98-Arg-112 in 6 N HCl at 110 degrees C gave a considerable amount of beta-aspartylglycine. Therefore, it was concluded that two-thirds of the protein obtained from this reaction possessed the beta-aspartylglycyl sequence at Asp-101-Gly-102. As a result, we obtained four lysozymes from this reaction, the derivative with the beta-aspartyl sequence at Asp-101 (101-beta-lysozyme), the cross-linked derivative between Lys-13 and Leu-129 (CL-lysozyme), the CL-lysozyme derivative with the beta-aspartyl sequence at Asp-101 (101-beta-CL-lysozyme), and native lysozyme. In the ethyl esterification of Asp-52 in lysozyme with triethyloxonium fluoroborate [Parsons, S. M., Jao, L., Dahlquist, F. W., Borders, C. L., Jr., Groff, T., Racs, J., & Raftery, M. A. (1969) Biochemistry 8, 700-712; Parsons, S. M., & Raftery, M. A. (1969) Biochemistry 8, 4199-4205], the same bond rearrangement was detected in the same ratio.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthetic and natural Escherichia coli free lipid A express identical endotoxic activities

The recently chemically synthesized Escherichia coli lipid A and the natural free lipid A of E. coli were compared with respect to their endotoxic activities in the following test systems: lethal toxicity, pyrogenicity, local Shwartzman reactivity, Limulus amoebocyte lysate gelation capacity, tumour necrotizing activity, B cell mitogenicity, induction of prostaglandin synthesis in macrophages, and antigenic specificity. It was found that synthetic and natural free lipid A exhibit identical activities and are indistinguishable in all tests.     

Aminoacyl-tRNA exclusively in the 3'-isomeric form is bound to polypeptide chain elongation factor Tu

2' and 3'-O-(N-acetyl-L-phenylalanyl)adenosine (Ac-Phe-Ado) were chemically synthesized. These two isomers were clearly separated from each other by high-performance liquid chromatography (HPLC). From the two isomers of [3H]Phe-tRNA in equilibrium, Ac-[3H]Phe-Ado was prepared, without any change in the 2'/3'-isomer ratio, by acetylation of the phenylalanyl residue with acetic anhydride followed by digestion with pancreatic RNase A. By HPLC analysis of this preparation of Ac-[3H]Phe-Ado, the abundance ratio of the 2'-isomer and the 3'-isomer of [3H]Phe-tRNA was found to be 0.20:0.80. Further, [3H]Phe-tRNA was bound to Escherichia coli polypeptide chain elongation factor Tu (EF-Tu) with the ligand of GTP or guanosine 5'-[beta, gamma-imido]triphosphate (GMP-P(NH)P). The ternary complex was treated with phenol and acetic anhydride, and then digested with pancreatic RNase A. By HPLC analysis of Ac-[3H]Phe-Ado, the abundance ratio of the 2'-isomer and the 3'-isomer of [3H]Phe-tRNA was determined to be 0.07:0.93 in the complex with EF-Tu.GTP and 0.04:0.96 in the complex with EF-Tu.GMP-P(NH)P. These results clearly indicate that the 3'-isomer, rather than the 2'-isomer, of aminoacyl-tRNA is exclusively involved in the ternary complex.     

Intramolecular cross-linkage of lysozyme. Imidazole catalysis of the formation of the cross-link between lysine-13 (epsilon-amino) and leucine-129 (alpha-carboxyl) by carbodiimide reaction

The salt bridge between Lys-13 (epsilon-NH3+) and Leu-129 (alpha-COO-) in lysozyme was converted to an amide bond by 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride (EDC) reaction in the presence of imidazole (0.3-1 M) at pH 5 and room temperature, followed by dialysis at pH 10. Absence of imidazole under a similar condition did not give this intramolecularly cross-linked lysozyme derivative (CL-lysozyme) but resulted in the formation of intermolecularly cross-linked lysozyme oligomers. From the mechanistic studies on the formation of CL-lysozyme, imidazole was suggested to play the following three roles. (1) Some carboxyl groups activated by EDC in lysozyme were converted to acylimidazole groups which protected them from the reaction with amino groups in other lysozyme molecules at pH 5. These could be hydrolyzed at pH 10 to regenerate free carboxyls. (2) High concentrations of imidazole (pH 5) increased the ionic strength of the solution which weakened the salt bridge in lysozyme and facilitated the activation of the alpha-carboxyl group by EDC. (3) The alpha-carboxyl group activated by EDC was converted to an acylimidazole group which could react with the epsilon-amino group of Lys-13 in the same molecule to form an amide bond. The last step may involve some conformational change of the backbone of lysozyme and be slower than the hydrolysis reaction of the alpha-carboxyl group activated by EDC itself. However, acylimidazole groups are stable against hydrolysis at pH 5. This may afford enough time to allow the epsilon-amino group of Lys-13 to attack the acylimidazole group of Leu-129.