Febs Letters

doi: 10.1016/0014-5793(89)81202-5pmid: N/A

Meer, L.Ter

doi: 10.1016/0014-5793(89)81203-7pmid: N/A

Gast, P.; Gottschalk, A.; Norris, J.R.; Closs, G.L.

doi: 10.1016/0014-5793(89)81204-9pmid: N/A

In the light‐induced charge separation that takes place in the bacterial photosynthetic reaction center protein a quinone molecule (Q) is reduced. The EPR spectrum of this reduced quinone is strongly broadened which is assumed to arise from interaction with the high spin (S=2) Fe2+, which is located near Q. Computer simulations of this EPR spectrum have been somewhat limited by the lack of structure in the EPR spectrum. The availability of single crystals of the reaction center protein offers the possibility to analyze the spectrum of the reduced iron‐quinone complex (FeQ−) in much greater detail than ever before. We have therefore measured the EPR spectrum of FeQ− using single crystals from the reaction center protein from the photosynthetic bacterium Rhodopseudomonas viridis. Transitions were obtained in the g value range of 1.7–1.9 for both crystal orientations, i.e. for rotation along and rotation perpendicular to the crystal's long axis. Strong line broadening was observed at many orientations, which could indicate a heterogeneity in the zerofield parameters of Fe2+.

Drachev, L.A.; Kaulen, A.D.; Zorina, V.V.

doi: 10.1016/0014-5793(89)81205-0pmid: N/A

Light‐scattering changes were found to accompany the bacteriorhodopsin photocycle in a suspension of purple membranes. A light‐scattering signal comprises three phases, connected with (i) bR → M transition, (ii) transition of M to P intermediate (other names: N,R350 intermediate), (iii) P → bR transition. Light‐scattering changes seem to result from changes in the purple membrane shape in response to the bacteriorhodopsin conformational changes during the photocycle.

Koretsky, Alan P.; Traxler, Beth A.

doi: 10.1016/0014-5793(89)81206-2pmid: 2646148

A cDNA encoding the B isozyme of creatine kinase (CKB) has been expressed in Escherichia coli from a fusion with lacZ carried by λgt11. Western blots indicate that a stable polypeptide with the appropriate mobility for the β‐galactosidase‐creatine kinase (β‐gal‐CKB) fusion protein cross‐reacts with both β‐gal and CKB antiserum. No significant CK activity is detected in control E. coli; however, extracts from cells containing the λgt11‐CKB construct have a CK activity of 1.54±0.07 μmol/min per mg protein. The fusion protein appears to provide this activity because immunoprecipitation of protein with β‐gal antiserum leads to a loss of CK activity from extracts. That the enzyme is active in vivo was demonstrated by detection of a phosphocreatine (PCr) peak in the 31P NMR spectrum from E. coli grown on medium supplemented with creatine. As in mammalian brain and muscle, the PCr peak detected was sensitive to the energy status of the E. coli.

Denizot, Yves; Dassa, Elie; Kim, Hee-Yong; Bossant, Marie-Jeanne; Salem, Norman; Thomas, Yolène; Benveniste, Jacques

doi: 10.1016/0014-5793(89)81207-4pmid: 2646144

Paf‐acether (paf) is a potent mediator of inflammatory diseases and septic shock. Using normal‐phase HPLC, a paf‐like activity was found in culture supernatants from E. coli. Prokaryotic paf exhibited the same biological and physico‐chemical properties as eukaryotic cells and synthetic paf. Further, reverse‐phase HPLC indicates that paf generated by bacteria is predominantly of the hexadecyl and octadecyl species. When cultures were supplemented with lyso‐paf, a dramatic increase in paf production was observed. The purity and molecular structure of bacterial paf were further characterized by mass spectral analysis. These results could be of importance considering the pathogenetic role of enterobacteria. Further, it appears that the competence to form and release paf is an early phylogenetic development.

Gillespie, J.I.; Giraldez, F.; Greenwell, J.R.

doi: 10.1016/0014-5793(89)81208-6pmid: 2537751

The effect of the mitogen bombesin on pHi in cells of the chick otic vesicle was studied using dual wavelength microspectrofluorimetric techniques. The results show that the bombesin did not produce an immediate alkalinization in quiescent otic vesicle cells nor a long‐term change in pHi in vesicles reactivated to grow in culture. The recovery of pHi from an acid load, caused by an NH4 pulse, involved both Na+/H+ exchange and Na+:HCO3 influx mechanisms, neither of which was influenced by bombesin. These observations do not fit with a general model whereby pHi is a universal signal for DNA replication and cell proliferation.

Gladhaug, Ivar P.; Christoffersen, Thoralf

doi: 10.1016/0014-5793(89)81209-8pmid: 2646145

n‐Butyrate was previously found to increase the epidermal growth factor (EGF) receptor binding in primary cultures of rat hepatocytes. We show here that butyrate and dexamethasone synergistically modulate the surface expression of the EGF receptors. The butyrate‐induced enhancement of high‐affinity EGF binding was only slight in the absence of glucocorticoid, but was strongly and dose‐dependently amplified by dexamethasone. Butyrate counteracted the inhibition by insulin of the dexamethasone‐induced increase in EGF binding. The results indicate that the glucocorticoid has a permissive effect on a butyrate‐sensitive process that determines the surface expression of the high‐affinity class of EGF receptors.

Nishida, Tsutomu; Nakai, Satoru; Kawakami, Takuma; Aihara, Koutoku; Nishino, Naoki; Hirai, Yoshikatsu

doi: 10.1016/0014-5793(89)81210-4pmid: 2646146

BSF‐2/IL‐6, GM‐CSF and IL‐1β mRNAs were induced by recombinant IL‐1 in human astrocytoma cell line U373MG. The induction of BSF‐2/IL‐6 and IL‐1β mRNAs did not require de novo protein synthesis while that of GM‐CSF mRNA required a newly synthesized protein. Dexamethasone inhibited the induction of these cytokine mRNAs by IL‐1. This process seems to require continued protein synthesis. These results suggest that the production of these cytokines are positively and negatively controlled by IL‐1 and glucocorticoids, respectively, in astrocytes.

Pliszka, Barbara; Rȩdowicz, Maria J.; Strzelecka-Gołaszewska, Hanna

doi: 10.1016/0014-5793(89)81211-6pmid: 2920822

Limited digestion of filamentous myosin with chymotrypsin at 0°C in the absence of divalent cations generates two forms of subfragment 1 (S1), with heavy chains of 95 kDa and 98 kDa. The difference is at the C‐terminal end of the chain. The 98 kDa form prevails, in contrast to the preparations obtained by digestion at room temperature which consist of the shorter species and only traces of the longer one. The results support the idea of a temperature‐dependent conformational transition at the head‐rod junctional region of the myosin heavy chain.