Pivotal Domain Research Articles

Crystal Structure of a Pivotal Domain of Human Syncytin-2, A 40 Million Years Old Endogenous Retrovirus Fusogenic Envelope Gene Captured by Primates

HERV-FRD is a human endogenous retrovirus that entered the human genome 40 million years ago. Its envelope gene, syncytin-2, was diverted by an ancestral host most probably because of its fusogenic property, for a role in placenta morphogenesis. It was maintained in a functional state in all primate branches as a bona fide cellular gene, submitted to a very low mutation rate as compared to infectious retrovirus genomes. The structure of the syncytin-2 protein thus provides a good insight into that of the oldest mammalian retroviral envelope. Here, we report the crystal structure of a central fragment of its "fossil" ectodomain, allowing a remarkable superposition with the structures of the corresponding domains of present-day infectious retroviruses, in spite of a more than 60% divergent sequence. These results suggest the existence of a unique structural solution selected by these proteins for their fusogenic function.

Colonialism and its Contradictions: Indians, Blacks and Social Power in Sixteenth and Seventeenth Century Mexico

Abstract This article examines patterns in the black/Indian relationship in Mexico during the sixteenth and seventeenth centuries. It focuses on microlevels of society and on the practice of power in two pivotal domains, one centered on instances of labor coercion and civil control, and the other on what was labelled “witchcraft.” The analysis suggests that Spanish colonialism embodied contradictions at its very foundations as it created sites of power for both blacks and Indians, who were alternately constituted as dominating and subordinated subjects vis‐à‐vis each other and the Spanish colonizers.

Identification of the essential regions for LukS- and H gamma II-specific functions of staphylococcal leukocidin and gamma-hemolysin.

Staphylococcal leukocidin and gamma-hemolysin consist of LukF and LukS for leudocidin and LukF and H gamma II for gamma-hemolysin. To identify the pivotal domain(s) of LukS and H gamma II responsible for their specific cytolytic activities, a series of chimeric genes (lukS/hlg2) were constructed and expressed in Escherichia coli. The results indicate that the C-terminal 24-residue and the N-terminal 57-residue segments of LukS and H gamma II, respectively, are the essential regions for the LukS and H gamma II functions.