Trophic models and short-term dynamic simulations for benthic-pelagic communities at Banco Chinchorro Biosphere Reserve (Mexican Caribbean): a conservation case

Banco Chinchorro is the largest reef in the Mexican Caribbean. Historically, spiny lobster, queen conch and over 20 other reef species have been exploited here. Multispecies intervention management from an ecosystem perspective has been developed in this area; however, an assessment of the effects of such practices on ecosystem health is required. Five quantitative trophic models were constructed using Ecopath with Ecosim. The results show that, in terms of biomass, benthic autotrophs are the dominant group in all communities. Ecosystem Network Analysis indices showed that Cueva de Tiburones was the most mature, developed, complex and healthy subsystem, but, El Colorado and La Baliza were the subsystems most resistant to disturbances. The fisheries mainly concentrate on primary (La Baliza and Cueva de Tiburones sites) and secondary consumers (La Caldera, Chancay, and El Colorado). The greatest propagation of direct and indirect effects, estimated by Mixed Trophic Impacts and Ecosim simulations, were generated by the benthic autotrophs, small benthic epifauna, benthic-pelagic carnivorous fish and benthic carnivorous fish, among others. In contrast, the System Recovery Time showed different patterns among subsystems, indicating several compartments that reduce resilience. Considering the structure, dynamics, trophic functioning and ecosystem health of Banco Chinchorro, its ecological heterogeneity highlights the need for the design of a specific (by subsystem) management strategy, particularly because different species or functional groups present greater sensitivity to human interventions in each community

Structural and mechanistic insights into the catalytic-domain-mediated short-range glycosylation preferences of GalNAc-T4

17 pags, 4 figs, 2 tabsMucin-type O-glycosylation is initiated by a family of polypeptide GalNAc-transferases (GalNAc-Ts) which are type-II transmembrane proteins that contain Golgi luminal catalytic and lectin domains that are connected by a flexible linker. Several GalNAc-Ts, including GalNAc-T4, show both long-range and short-range prior glycosylation specificity, governed by their lectin and catalytic domains, respectively. While the mechanism of the lectin-domain-dependent glycosylation is well-known, the molecular basis for the catalytic-domain-dependent glycosylation of glycopeptides is unclear. Herein, we report the crystal structure of GalNAc-T4 bound to the diglycopeptide GAT GAGAGAGT TPGPG (containing two α-GalNAc glycosylated Thr (T ), the PXP motif and a "naked" Thr acceptor site) that describes its catalytic domain glycopeptide GalNAc binding site. Kinetic studies of wild-type and GalNAc binding site mutant enzymes show the lectin domain GalNAc binding activity dominates over the catalytic domain GalNAc binding activity and that these activities can be independently eliminated. Surprisingly, a flexible loop protruding from the lectin domain was found essential for the optimal activity of the catalytic domain. This work provides the first structural basis for the short-range glycosylation preferences of a GalNAc-T.We thank synchrotron radiation sources DLS (Oxford) and in particular beamline I03 (experiment number MX10121-15). We thank ARAID, MEC (CTQ2013-44367-C2-2-P, BFU2016-75633-P, CTQ2015-67727-R, CTQ2015-70524-R, and CTQ2017-85496-P), AGAUR (SGR2017-1189), the National Institutes of Health (R01-GM113534, and instrument Grant GM113534-01S to T. A. Gerken), the Danish National Research Foundation (DNRF107), the FCT-Portugal [UID/Multi/04378/2013 cofinanced by the FEDER (POCI- 01-0145-FEDER-007728)], and the DGA (E34_R17) for financial support. I. Compañón thanks Universidad de La Rioja for the FPI grant. F. Marcelo thanks FCT-Portugal for IF Investigator grant (IF/00780/2015) and PTNMR supported by Project 022161. E. Lira-Navarrete acknowledges her postdoctoral EMBO fellowship ALTF 1553-2015 cofunded by the European Commission (LTFCOFUND2013, GA-2013-609409) and Marie Curie Actions. H. Coelho and J. Jiménez-Barbero thank EU for the TOLLerant project. The research leading to these results has also received funding from the FP7 (2007−2013) under BioStruct-X (Grant agreement 283570 and BIOSTRUCTX_5186). We would also like to acknowledge the assistance of Juwan Lee in obtaining the GalNAc-T4 random peptide motif