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Enzyme Selectivity Fine-Tuned through Dynamic Control of a Loop.

ABSTRACT: Allostery has been revealed as an essential property of all proteins. For enzymes, shifting of the structural equilibrium distribution at one site can have substantial impacts on protein dynamics and selectivity. Promising sites of remotely shifting such a distribution by changing the dynamics would be at flexible loops because relatively large changes may be achieved with minimal modification of the protein. A ligand-selective change of binding affinity to the active site of cyclophilin is presented involving tuning of the dynamics of a highly flexible loop. Binding affinity is increased upon substitution of double Gly to Ala at the hinge regions of the loop. Quenching of the motional amplitudes of the loop slightly rearranges the active site. In particular, key residues for binding Phe60 and His126 adopt a more fixed orientation in the bound protein. Our system may serve as a model system for studying the effects of various time scales of loop motion on protein function tuned by mutations.

SUBMITTER: Vogeli B

PROVIDER: S-EPMC4760428 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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Enzyme Selectivity Fine-Tuned through Dynamic Control of a Loop.

Vögeli Beat B Bibow Stefan S Chi Celestine N CN

Angewandte Chemie (International ed. in English) 20160128 9

Allostery has been revealed as an essential property of all proteins. For enzymes, shifting of the structural equilibrium distribution at one site can have substantial impacts on protein dynamics and selectivity. Promising sites of remotely shifting such a distribution by changing the dynamics would be at flexible loops because relatively large changes may be achieved with minimal modification of the protein. A ligand-selective change of binding affinity to the active site of cyclophilin is pres ...[more]

PMID: 26822756

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Project description:Background: The histone demethylase KDM1A is a multi-faceted regulator of critical developmental processes, including mesodermal and cardiac tube formation during mice gastrulation. The fine-tuning of KDM1A splicing has been linked to regulating the transcriptional program of excitable cells such as neurons. However, it is unknown whether modulating the expression of KDM1A isoforms is crucial for the specification and maintenance of cell identity of other cell types sensitive to electrical cues such as the cardiomyocytes. Objective: We investigated the role of ubKDM1A and KDM1A+2a ubiquitous splice variants during cardiomyogenesis and evaluated their impact on the regulation of cardiac differentiation in vitro. Methods and Results: We discovered a temporal modulation of ubKDM1A and KDM1A+2a isoform levels during human and mouse fetal cardiac development. Therefore, we generated human embryonic stem cells (hESCs) exclusively devoid of one or both isoforms and assessed their potential to derive cardiomyocytes. KDM1A depletion severely impaired cardiac differentiation. Conversely, KDM1A+2a-/- hESCs give rise to functional cardiomyocytes, displaying increased beating amplitude and frequency compared to wild-type cells. Transcriptomic profiling revealed that KDM1A-/- cardiomyocytes fail to activate an effective cardiac transcriptional program, while the depletion of KDM1A+2a enhances the expression of key cardiogenic markers. Notably, the impaired cardiac differentiation of KDM1A-/- cells can be rescued by re-expressing ubKDM1A or catalytically deficient ubKDM1A-K661A, but not by KDM1A+2a or KDM1A+2a-K661A. These data demonstrate a divergent role of the two KDM1A isoforms that is independent of their enzymatic activity. Through an exhaustive biochemical and genome-wide binding characterization, we excluded that the opposite ubKDM1A- and KDM1A+2a-mediated regulation of cardiac differentiation resides into differential substrate specificity, H3K4 demethylation efficiency, core-partners binding affinity, or alternative genome binding profiles. Conclusions: Our findings suggest the existence of a divergent scaffolding role of KDM1A splice variants during hESC differentiation into cardiomyocytes.

Project description:A diversity of arthropods (myrmecophiles) thrives within ant nests, many of them unmolested though some, such as the specialized Eucharitidae parasitoids, may cause direct damage to their hosts. Ants are known to discriminate between nestmates and non-nestmates, but whether they recognize the strength of a threat and their capacity to adjust their behavior accordingly have not been fully explored. We aimed to determine whether Ectatomma tuberculatum ants exhibited specific behavioral responses to potential or actual intruders posing different threats to the host colony and to contribute to an understanding of complex ant-eucharitid interactions. Behavioral responses differed significantly according to intruder type. Ants evicted intruders that represented a threat to the colony's health (dead ants) or were not suitable as prey items (filter paper, eucharitid parasitoid wasps, non myrmecophilous adult weevils), but killed potential prey (weevil larvae, termites). The timing of detection was in accordance with the nature and size of the intruder: corpses (a potential source of contamination) were detected faster than any other intruder and transported to the refuse piles within 15 min. The structure and complexity of behavioral sequences differed among those intruders that were discarded. Workers not only recognized and discriminated between several distinct intruders but also adjusted their behavior to the type of intruder encountered. Our results confirm the previously documented recognition capabilities of E. tuberculatum workers and reveal a very fine-tuned intruder discrimination response. Colony-level prophylactic and hygienic behavioral responses through effective removal of inedible intruders appears to be the most general and flexible form of defense in ants against a diverse array of intruders. However, this generalized response to both potentially lethal and harmless intruders might have driven the evolution of ant-eucharitid interactions, opening a window for parasitoid attack and allowing adult parasitoid wasps to quickly leave the natal nest unharmed.

Dataset Information

Enzyme Selectivity Fine-Tuned through Dynamic Control of a Loop.

Publications

Enzyme Selectivity Fine-Tuned through Dynamic Control of a Loop.

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