X-Ray Structure of Yeast Inorganic Pyrophosphatase Complexed with Manganese and Phosphate

The three-dimensional structure of the manganese-phosphate complex of inorganic pyrophosphatase from Saccharomyces cerevisiae has been refined to an R factor of 19.0% at 2.4-Å resolution. X-ray data were collected from a single crystal using an imaging plate scanner and synchrotron radiation. There is one dimeric omolecule in the asymmetric unit. The upper estimate of the root-mean-square coordinate error is 0.4 Å using either the σA plot or the superposition of the two crystallographically independent subunits. The good agreement between the coordinates of the two subunits, which were not subjected to non-crystallographic symmetry restraints, provides independent validation of the structure analysis. The active site in each subunit contains four manganese ions and two phosphates. The manganese ions are coordinated by the side chains of aspartate and glutamate residues. The phosphate groups, which were identified on the basis of their local stereochemistry, interact either directly or via water molecules with manganese ions and lysine, arginine, and tyrosine side chains. The phosphates are bridged by two of the manganese ions. The outer phosphate is exposed to solvent. The inner phosphate is surrounded by all four manganese ions. The ion-binding sites are related to the order of binding previously established from kinetic studies. A hypothesis for the transition state of the catalytic reaction is put forward

FORESTS AND SOCIETY – RESPONDING TO GLOBAL DRIVERS OF CHANGERegional Examples of Forest Related Challenges and Opportunities 14 Sustainability of Boreal Forests and Forestry in a Changing Environment

Abstract: The circumpolar boreal forest is the fourth largest terrestrial biome on the planet. It is entering a period of relatively rapid transition, propelled by climate change and economic development. Warming conditions threaten to alter processes as diverse as permafrost retention, insect outbreaks, and transportation. Thawing permafrost and increased levels of natural and anthropogenic disturbance may result in net releases of carbon dioxide and methane, while forest cover with greater biomass can be expected to expand onto the arctic tundra. Human use in some parts of northern forests is becoming more centralised and industrialised, with cumulative impacts from hydroelectric development, the oil and gas sector, mining, timber harvesting, and transportation. Communities tend to be widely spaced, and are either highly dependent on resource-based commodity exports or on subsistence-based lifestyles supported by local biodiversity. Efforts are underway in many jurisdictions to curtail illegal logging and environmentally damaging industrial development, to account for non-timber forest values in the course of forest management, and to promote the economic diversification of communities. In order to preserve the integrity of ecosystem processes, effort