The crystal structure of a conserved domain of nonstructural protein 3 (nsP3) from severe acute respiratory syndrome coronavirus (SARS-CoV) has been solved by single-wavelength anomalous dispersion to 1.4 A resolution. The structure of this "X" domain, seen in many single-stranded RNA viruses, reveals a three-layered alpha/beta/alpha core with a macro-H2A-like fold. The putative active site is a solvent-exposed cleft that is conserved in its three structural homologs, yeast Ymx7, Archeoglobus fulgidus AF1521, and Er58 from E. coli. Its sequence is similar to yeast YBR022W (also known as Poa1P), a known phosphatase that acts on ADP-ribose-1''-phosphate (Appr-1''-p). The SARS nsP3 domain readily removes the 1'' phosphate group from Appr-1''-p in in vitro assays, confirming its phosphatase activity. Sequence and structure comparison of all known macro-H2A domains combined with available functional data suggests that proteins of this superfamily form an emerging group of nucleotide phosphatases that dephosphorylate Appr-1''-p.
, the communist Khmer Rouge marched into Phnom Penh and established Democratic Kampuchea. Declaring an end to "over two thousand years of Cambodian history," 1 Khmer Rouge leader Pol Pot announced a new beginning, referred to metaphorically by scholars of the period as the "Year Zero." 2 The "new Cambodia" lasted exactly three years, eight months, and twenty days, during which time the people of Cambo dia were subjected to a cataclysmic social experiment as part of what one his torian has termed "the world's most radical... revolution." 3 Many first-hand accounts and scholarly analyses based on interviews with refugees describe the horrifying events of the late 1970s. 4 Closing Cambodia off from nearly all communication with the outside world, the Khmer Rouge evacuated Phnom Penh and all other urban centers, and city dwellers were sent to the countryside where they were forced to work in agri
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