Porin channel triplets merge into single outlets in Escherichia coli outer membranes

Previous observations on the structural and functional properties of porin, the matrix protein of Escherichia coli, have indicated that the channel-forming trimers span the outer membranes of the bacterial cell, forming a molecular sieve. By using electron microscopy and image reconstruction, we demonstrate here that three channels on the outer surface of the cell merge into a single channel at the periplasmic face. Conductance measurements using conditions under which single activated triplets could be observed led us to conclude that the three individual consecutive closing steps reflect three channels within a single trimeric unit. Statistical analysis of conductance levels revealed that the first relaxation step is distinctly smaller than the two subsequent channel closings. This functional observation can be explained if the channels of porin trimers coalesce.     

Genetic variation of α-glycerophosphate — dehydrogenase isoenzymes in clupeoid and salmonoid fish

Zusammenfassung Die Isoenzyme der -GPDH lassen bei diploiden (Hering, Stint) und tetraploiden (Regenbogen-, Bachforelle) Fischen der OrdnungIsospondyli auf jeweils 3 verschiedene Genloci schliessen. Die stammesgeschichtlichen Beziehungen zwischen den verschiedenen Untereinheiten werden kurz diskutiert.

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Supported by the Deutsche Forschungsgemeinschaft.     

Adenylylation control by intra- or intermolecular active-site obstruction in Fic proteins

Fic proteins that are defined by the ubiquitous FIC (filamentation induced by cyclic AMP) domain are known to catalyse adenylylation (also called AMPylation); that is, the transfer of AMP onto a target protein. In mammalian cells, adenylylation of small GTPases through Fic proteins injected by pathogenic bacteria can cause collapse of the actin cytoskeleton and cell death. It is unknown how this potentially deleterious adenylylation activity is regulated in the widespread Fic proteins that are found in all domains of life and that are thought to have critical roles in intrinsic signalling processes. Here we show that FIC-domain-mediated adenylylation is controlled by a conserved mechanism of ATP-binding-site obstruction that involves an inhibitory α-helix (α(inh)) with a conserved (S/T)XXXE(G/N) motif, and that in this mechanism the invariable glutamate competes with ATP γ-phosphate binding. Consistent with this, FIC-domain-mediated growth arrest of bacteria by the VbhT toxin of Bartonella schoenbuchensis is intermolecularly repressed by the VbhA antitoxin through tight binding of its α(inh) to the FIC domain of VbhT, as shown by structure and function analysis. Furthermore, structural comparisons with other bacterial Fic proteins, such as Fic of Neisseria meningitidis and of Shewanella oneidensis, show that α(inh) frequently constitutes an amino-terminal or carboxy-terminal extension to the FIC domain, respectively, partially obstructing the ATP binding site in an intramolecular manner. After mutation of the inhibitory motif in various Fic proteins, including the human homologue FICD (also known as HYPE), adenylylation activity is considerably boosted, consistent with the anticipated relief of inhibition. Structural homology modelling of all annotated Fic proteins indicates that inhibition by α(inh) is universal and conserved through evolution, as the inhibitory motif is present in ～90% of all putatively adenylylation-active FIC domains, including examples from all domains of life and from viruses. Future studies should reveal how intrinsic or extrinsic factors modulate adenylylation activity by weakening the interaction of α(inh) with the FIC active site.     

The first twisted-wing parasitoid in Eocene amber from north-eastern China (Strepsiptera: Myrmecolacidae)

An Early Eocene amber twisted-wing parasitoid (Strepsiptera) is described and figured from the Fushun Coalfield in north-eastern China, representing the first record of this order for the Tertiary of Asia and the second extinct genus of Myrmecolacidae. Kronomyrmecolax fushunicus gen. et sp. nov. is represented by a single male which is distinguished from other living and fossil myrmecolacids, particularly Palaeomyrmecolax Kulicka, in middle Eocene Baltic amber. The genera differ in details of hind wing venation and antennal morphology.     

Multimodal Brain-Computer Interfaces

A critical parameter of brain-computer interfaces(BCIs) is the number of dimensions a user can control independently.One way to increment this number without increasing the mental effort required to operate the system is to stimulate several sensory modalities simultaneously,and to distinguish brain activity patterns when the user focuses attention to different elements of this multisensory input.In this article we show how shifting attention between simultaneously presented tactile and visual stimuli affects the electrical brain activity of human subjects,and that this signal can be used to augment the control information from the two uni-modal BCI subsystems.     

Identification of serotonin M-receptor subtypes and their specific blockade by a new class of drugs

We describe a new class of drugs that selectively block serotonin M-receptors on peripheral neurones. Because of their high affinity, some of these drugs are the most potent of any pharmacological class yet reported. They have allowed the identification of three M-receptor subtypes, one of which is responsible for mediating the painful effects of serotonin in humans.