The Self-Organization of Social Movements

The New Social Movement Approach and the Resource Mobilization Approach are the dominant approaches in social movement research. They focus either on macro-aspects and externalism or on micro-aspects and internalism. This paper suggests that the notion of self-organization is one way of taking into account both internal and external, structural- and action-based aspects of social movements and that it allows a dynamic concept of protest. The emergence of social movements is not determined, but a complex result of crisis, resource mobilization, cognitive mobilization, self-production—searching for singular laws of the emergence of movements is an expression of one-dimensional, linear, and deterministic thinking. Protest and social problems are non-linearly related. Social movements are part of the civil society system, by producing alternative topics and demands, they guarantee the dynamic of the political system. Existing system-theoretic approaches on social movements (Luhmann, Japp, Ahlemeyer, Hellmann) are rather uncritical and ignore the productive relationship between human actors and social structures in processes of social self-organization. Social movements are dynamic communication systems that permanently react to political and societal events with self-organized protest practices and protest communications that result in the emergence and differentiation (production and reproduction) of protest structures (events, oppositional topics, alternative values, regularized patterns of interaction and organization). The dynamic of social movements is based on the permanent emergence and mutual production of protest practices and protest structures. The self-organization of a social movement is a vivid process, it is based on the permanent movement and differentiation of actors and structures that communicate public protest, a social movement is only a movement, as long as it communicates protest and moves itself. In critical phases of protest new social systems of protest emerge whose form, content and effects are not determined, but dependent upon old structures, i.e., old structures enable and constrain new structures. The emergence of new protest issues, methods, identities, structures, and organizational forms starts as singular innovation, if it is widely imitated then it spreads within the protest system and transforms the system as a whole. In terms of Hegelian dialectics this means that novel qualities sublate the old structure of the total system, i.e., the system is transformed, reaches a higher level, incorporates old qualities, and creates new qualities. In critical phases protest can spontaneously and quickly spread and intensify itself. This reflects the idea of complexity thinking that small causes can spontaneously have large effects. The notion of self-organization as the idea of the networked, co-operative, synergetic production of emergent qualities and systems should be employed in order to arrive at a dynamic concept of protest. In order to reflect the increasing complexity of society and the emergence of a stratified knowledge society, a multidimensional model of class that is structurally coupled to the concept of social movements is suggested.

Active-site remodelling in the bifunctional fructose-1,6-bisphosphate aldolase/phosphatase

Fructose-1,6-bisphosphate (FBP) aldolase/phosphatase is a bifunctional, thermostable enzyme that catalyses two subsequent steps in gluconeogenesis in most archaea and in deeply branching bacterial lineages. It mediates the aldol condensation of heat-labile dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GAP) to FBP, as well as the subsequent, irreversible hydrolysis of the product to yield the stable fructose-6-phosphate (F6P) and inorganic phosphate; no reaction intermediates are released. Here we present a series of structural snapshots of the reaction that reveal a substantial remodelling of the active site through the movement of loop regions that create different catalytic functionalities at the same location. We have solved the three-dimensional structures of FBP aldolase/phosphatase from thermophilic Thermoproteus neutrophilus in a ligand-free state as well as in complex with the substrates DHAP and FBP and the product F6P to resolutions up to 1.3??. In conjunction with mutagenesis data, this pinpoints the residues required for the two reaction steps and shows that the sequential binding of additional Mg(2+) cations reversibly facilitates the reaction. FBP aldolase/phosphatase is an ancestral gluconeogenic enzyme optimized for high ambient temperatures, and our work resolves how consecutive structural rearrangements reorganize the catalytic centre of the protein to carry out two canonical reactions in a very non-canonical type of bifunctionality.     

An oxygenase that forms and deoxygenates toxic epoxide

Catabolism may give rise to toxic intermediates that compromise cell vitality, such as epoxide formation in the recently elucidated and apparently universal bacterial coenzyme A (CoA)-dependent degradation of phenylacetic acid. This compound is central to the catabolism of a variety of aromatics, such as phenylalanine, lignin-related compounds or environmental contaminants. The key phenylacetyl-CoA monooxygenase (epoxidase) of the pathway, PaaABCE, is also connected to the production of various primary and secondary metabolites, as well as to the virulence of certain pathogens. However, the enzyme complex has so far not been investigated in detail. Here we characterize the bacterial multicomponent monooxygenase PaaABCE that, surprisingly, not only transforms phenylacetyl-CoA into its ring-1,2-epoxide, but also mediates the NADPH-dependent removal of the epoxide oxygen, regenerating phenylacetyl-CoA with formation of water. We provide evidence for a catalytic di-iron centre that is probably the key to the unprecedented deoxygenation of an organic compound by an oxygenase. Presumably, the bifunctionality is vital to avoid toxic intracellular epoxide levels if the subsequent catabolic steps are impeded. Our data suggest that detoxification is assisted by two thioesterases (PaaI and PaaY) forming non-reactive breakdown products. Hence, PaaABCE may harbour an intrinsic escape mechanism from its own toxic product and represents the archetype of a bifunctional oxygenase/deoxygenase. Analogous reactions may possibly be catalysed by other di-iron epoxidases.     

The duration of antigen receptor signalling determines CD4+ versus CD8+ T-cell lineage fate

Signals elicited by binding of the T-cell antigen receptor and the CD4/CD8 co-receptor to major histocompatibility complex (MHC) molecules control the generation of CD4+ (helper) or CD8+ (cytotoxic) T cells from thymic precursors that initially express both co-receptor proteins. These precursors have unique, clonally distributed T-cell receptors with unpredictable specificity for the self-MHC molecules involved in this differentiation process. However, the mature T cells that emerge express only the CD4 (MHC class II-binding) or CD8 (MHC class I-binding) co-receptor that complements the MHC class-specificity of the T-cell receptor. How this matching of co-receptor-defined lineage and T-cell-receptor specificity is achieved remains unknown, as does whether signalling by the T-cell receptors, co-receptors and/or general cell-fate regulators such as Notch-1 contributes to initial lineage choice, to subsequent differentiation processes or to both. Here we show that the CD4 versus CD8 lineage fate of immature thymocytes is controlled by the co-receptor-influenced duration of initial T-cell receptor-dependent signalling. Notch-1 does not appear to be essential for this fate determination, but it is selectively required for CD8+ T-cell maturation after commitment directed by T-cell receptors. This indicates that the signals constraining CD4 versus CD8 lineage decisions are distinct from those that support subsequent differentiation events such as silencing of co-receptor loci.     

Scratching the surface of skin development

The epidermis and its appendages develop from a single layer of multipotent embryonic progenitor keratinocytes. Embryonic stem cells receive cues from their environment that instruct them to commit to a particular differentiation programme and generate a stratified epidermis, hair follicles or sebaceous glands. Exciting recent developments have focused on how adult skin epithelia maintain populations of stem cells for use in the natural cycles of hair follicle regeneration and for re-epithelialization in response to wounding.