Sialyltransferases are key enzymes involved in the biosynthesis of biologically and pathologically important sialic acid-containing molecules in nature. Binary X-ray crystal structures of a multifunctional Pasteurella multocida sialyltransferase (Delta24PmST1) with a donor analogue CMP-3F(a)Neu5Ac or CMP-3F(e)Neu5Ac were determined at 2.0 and 1.9 A resolutions, respectively. Ternary X-ray structures of the protein in complex with CMP or a donor analogue CMP-3F(a)Neu5Ac and an acceptor lactose have been determined at 2.0 and 2.27 A resolutions, respectively. This represents the first sialyltransferase structure and the first GT-B-type glycosyltransferase structure that is bound to both a donor analogue and an acceptor simultaneously. The four structures presented here reveal that binding of the nucleotide-activated donor sugar causes a buried tryptophan to flip out of the protein core to interact with the donor sugar and helps define the acceptor sugar binding site. Additionally, key amino acid residues involved in the catalysis have been identified. Structural and kinetic data support a direct displacement mechanism involving an oxocarbenium ion-like transition state assisted with Asp141 serving as a general base to activate the acceptor hydroxyl group.

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The archaeology of the nineteenth-century Chinese diaspora is a well-developed archaeological subfield, but research on Chinese migrants’ homelands is lacking. Survey of a qiaoxiang (home village) in China's Pearl River Delta provides the first archaeological evidence from a home village of Chinese migrants. Transnational comparative analysis with collections recovered from Chinese diaspora settlements reveals stark differences in the use of China-produced goods between qiaoxiang and Chinese settlements abroad. Qiaoxiang residents primarily used locally produced ceramics, while residents of Chinese diaspora settlements consumed ceramics produced in Gaobei and Jingdezhen, major pottery centers located in northeast Guangdong Province and Jiangxi Province, hundreds of kilometers to the north. Additionally, qiaoxiang residents were engaged in global networks of consumption, using British refined earthenwares and other products produced in Europe and the United States. These findings challenge the common assumption made in diaspora research that artifacts produced in migrants’ homelands are evidence of tradition, while those produced in migrants’ adopted countries are evidence of culture change. Instead, the results of qiaoxiang archaeology indicate the significance of nonstate actors, especially import-export companies, in shaping the material worlds of both homeland and diaspora communities. (Spanish abstract available as Supplemental Text 1.)