The NADH-binding subunit of respiratory chain complex I is nuclear-encoded in plants and identified only in mitochondria

In higher plants, genes for subunits of respiratory chain complex I (NADH:ubiquinone oxidoreductase) have so far been identified solely in organellar genomes. At least nine subunits are encoded by the mitochondrial DNA and 11 homologues by the plastid DNA. One of the 'key' components of complex I is the subunit binding the substrate NADH. The corresponding gene for the mitochondrial subunit has now been cloned and identified in the nuclear genome from potato ( Solanum tuberosum ). The mature protein consists of 457 amino acids and is preceded by a mitochondrial targeting sequence of 30 amino acids. The protein is evolutionarily related to the NADH-binding subunits of complex I from other eukaryotes and is well conserved in the structural domains predicted for binding the substrate NADH, the FMN and one iron-sulphur cluster. Expression examined in different potato tissues by Northern blot analysis shows the highest steady-state mRNA levels in flowers.
Precursor proteins translated in vitro from the cDNA are imported into isolated potato mitochondria in a ΔΨ-dependent manner. The processed translation product has an apparent molecular mass of 55 kDa, identical to the mature protein present in the purified plant mitochondrial complex I. However, the in-vitro translated protein is not imported into isolated chloroplasts. To further investigate whether the complex I-like enzyme in chloroplasts contains an analogous subunit for binding of NAD(P)H, different plastid protein fractions were tested with a polyclonal antiserum directed against the bovine 51 kDa NADH-binding subunit. In none of the different thylakoid or stroma protein fractions analysed were specific crossreactive polypeptides detected. These results are discussed particularly with respect to the structure of a potential complex I in chloroplasts and the nature of its acceptor site.     

Determination of substrate utilization patterns of soil microbial communities: An approach to assess population changes after hydrocarbon pollution

Abstract: Changes in hydrocarbon content in soils resulted in characteristic shifts of the substrate utilization patterns as tested with the Biolog system. The altered patterns of substrate utilization corresponded to similar changes in abundance of hydrocarbon-utilizing bacteria and the occurrence of specific bacterial groups in the soils. Substrate utilization patterns as recorded with the Biolog system are suitable for rapidly assessing dynamics of autochthonous soil communities and evaluating their biodegradative potential.     

MinCD-independent inhibition of cell division by a protein that fuses MalE to the topological specificity factor MinE.

We report that MinE, the topological specificity factor of cell division in Escherichia coli, inhibits septation when fused to the C terminus of the maltose-binding protein MalE. This contrasts with overexpression of MinE alone, which affects growth but has no effect on division. Inhibition by MalE-MinE was minCD independent and depended on MinE segments involved in dimerization and prevention of MinCD division inhibition. The SOS and the heat shock responses were not involved, suggesting that the inhibition comes from a direct interaction of MalE-MinE with the septation apparatus. MalE-MinE lethality was suppressed by overexpression of ftsZ, as well as by overexpression of ftsN, a suppressor of temperature-sensitive mutations in genes ftsQ, ftsA, and ftsI. We also report that high-level synthesis of MalE disturbs nucleoid partitioning.     

Inactivation of the (+) gamete agglutinin during the mating-type reaction in chlamydomonas

Sex cell contact in Chlamydomonas is due to complementary sex-specific glycoproteins (mating-type substances, MTSs). Their interaction causes an instantaneous but labile flagella agglutination between sexually different gametes. The dynamic nature of this contact permits partner exchange between agglutinated gametes and accounts for the transitoriness of the contact, flagella adhesion being terminated upon ensuing pairing. This paper describes molecular events that underlie the adhesion potential of differentiated (+) gametes. In the contact-establishing interaction with its receptors on the (?) flagella, the agglutinin of differentiated (+) gametes is inactivated. Compensating for this inactivation, the adhesion potential of gametes in agglutination is sustained by continuous replenishment of the inactivated MTS by newly synthesized units. If this glycoprotein neosynthesis is blocked by tunicamycin (TUM), the adhesiveness of differentiated (+) gametes ceases. It is postulated that this complex interaction with incapacitation and neosynthesis forms the basis of the dynamic nature of the flagella contact and eventually accounts for its termination at pairing.     

Bacteriochlorophyll a cation radical in solution and in reaction centers of Rhodopseudomonas sphaeroides. Resonance Raman scattering

Resonance Raman spectra of the π-cation of bacterio-chlorophyll a in solution at 30 K are reported and discussed. Outer C

C bonds of the pyrroles and the methine bridges are weakened by the ionization, while C

N and Mg-N bonds remain essentially unaffected. Resonance Raman spectra of reaction centers suggest that the positive charge on P-870⁺ should be localized on a single bacteriochlorophyll molecule by the lifetime of the scattering process (≈ 10^?13 s).     

Tentative immunohistochemical demonstration of melatonin in the rat pineal gland

Summary In the present study an attempt was made to demonstrate melatonin in the rat pineal gland by means of immunohistochemistry. The anti-body used was raised against 5-methoxy-N-acetyltryptophan which is chemically similar to melatonin. Specific fluorescence was demonstrable only in pineals from rats killed during the night, when melatonin formation is high. It was restricted to parenchymal cells lying in a marginal zone of the organ. These results are discussed in relation to a subdivision of the pineal parenchyma into cortical and medullary areas.Supported by a grant of the Deutsche Forschungsgemeinschaft (VO 135/4) within the Schwerpunktprogramm Neuroendokrinologie