| 1. |
- Hong, Liang, et al.
(författare)
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Structure and Dynamics of a Compact State of a Multidomain Protein, the Mercuric Ion Reductase
- 2014
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Ingår i: Biophysical Journal. - : Elsevier BV. - 1542-0086 .- 0006-3495. ; 107:2, s. 393-400
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Tidskriftsartikel (refereegranskat)abstract
- The functional efficacy of colocalized, linked protein domains is dependent on linker flexibility and system compaction. However, the detailed characterization of these properties in aqueous solution presents an enduring challenge. Here, we employ a novel, to our knowledge, combination of complementary techniques, including small-angle neutron scattering, neutron spin-echo spectroscopy, and all-atom molecular dynamics and coarse-grained simulation, to identify and characterize in detail the structure and dynamics of a compact form of mercuric ion reductase (MerA), an enzyme central to bacterial mercury resistance. MerA possesses metallochaperone-like N-terminal domains (NmerA) tethered to its catalytic core domain by linkers. The NmerA domains are found to interact principally through electrostatic interactions with the core, leashed by the linkers so as to subdiffuse on the surface over an area close to the core C-terminal Hg(II)-binding cysteines. How this compact, dynamical arrangement may facilitate delivery of Hg(II) from NmerA to the core domain is discussed.
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| 2. |
- Liang, Yue, et al.
(författare)
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Brachiopods from the Latham Shale Lagerstätte (Cambrian Series 2, Stage 4) and Cadiz Formation (Miaolingian, Wuliuan), California
- 2022
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Ingår i: Journal of Paleontology. - : Cambridge University Press. - 0022-3360 .- 1937-2337. ; 96:1, s. 61-80
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Tidskriftsartikel (refereegranskat)abstract
- A moderately diverse assemblage of brachiopods from the Latham Shale Lagerstätte (Cambrian Series 2, upper Stage 4) and the upper Cadiz Formation (Miaolingian, Wuliuan), California is described in detail for the first time. The fauna includes both linguliform and rhynchonelliform brachiopods—Hadrotreta primaea (Walcott, 1902), Paterina prospectensis (Walcott, 1884), Dictyonina pannula (White, 1874), and Mickwitzia occidens Walcott, 1908; and Nisusia fulleri Mount, 1981 and Wimanella highlandensis (Walcott, 1886), respectively—together with olenellid trilobites and hyolithids. The fauna differs from other Cambrian Konservat-Lagerstätten (notably Cambrian Series 2 Chengjiang and Guanshan Lagerstätten, eastern Yunnan) in that the brachiopod shell valves in many cases are still preserved with their original mineralization. Moreover, the excellently preserved shale-hosted valves even include cases with exquisite epithelial cell molds, otherwise only seen in acid-etched material from carbonate rocks. The pitted ornamentation in D. pannula closely resembles that described from Ordovician linguliforms. The unusual preservation of N. fulleri provides important clues for ancestral composition of the brachiopod shell. The two articulated rhynchonelliform species probably represent the oldest records of this group from the west Laurentia. The fauna could also represent the earliest onset of the transition from the Cambrian Evolutionary Fauna (CEF) to the Paleozoic Evolutionary Fauna (PEF).
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| 3. |
- Duan, Xiaolin, et al.
(författare)
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Early Cambrian (Stage 4) brachiopods from the Shipai Formation in the Three Gorges area of South China
- 2021
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Ingår i: Journal of Paleontology. - : Cambridge University Press. - 0022-3360 .- 1937-2337. ; 95:3, s. 497-526
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Tidskriftsartikel (refereegranskat)abstract
- Diverse and abundant fossil taxa have been described in the lower Cambrian Shipai Formation in the Three Gorges area of Hubei Province, South China, but the taxonomy and diversity of the co-occurring brachiopod fauna are still far from clear. Here we describe the brachiopod fauna recovered from the Shipai Formation in the Three Gorges area of South China, including representatives of the subphylum Linguliformea: linguloids (Lingulellotreta ergalievi, Eoobolus malongensis, and Neobolidae gen. indet. sp. indet.), and an acrotretoid (Linnarssonia sapushanensis); and representatives from the subphylum Rhynchonelliformea: the calcareous-shelled Kutorginates (Kutorgina sinensis, Kutorgina sp., and Nisusia liantuoensis). This brachiopod assemblage and the first occurrence of Linnarssonia sapushanensis shell beds permit correlation of the Shipai Formation in the Three Gorges area of Hubei Province with the Stage 4 Wulongqing Formation in the Wuding area of eastern Yunnan. This correlation is further strengthened by the first appearance datum (FAD) of the rhynchonelliform brachiopod Nisusia in the upper silty mudstone of both the Shipai and Wulongqing formations. The new well-preserved material, derived from siliciclastic rocks, also gives critical new insights into the fine shell structure of L. sapushanensis. Microstructural studies on micromorphic acrotretoids (like Linnarssonia) have previously been restricted to fossils that were acid-etched from limestones. This is the first study to carry out detailed comparative ultrastructural studies on acrotretoid shells preserved in siliciclastic rocks. This work reveals a hollow tube and solid column microstructure in the acrotretoid shells from the Shipai Formation, which is likely to be equivalent of traditional column and central canal observed in shells dissolved from limestones.
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| 4. |
- Duan, Xiaolin, et al.
(författare)
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First report of acrotretoid brachiopod shell beds in the lower Cambrian (Stage 4) Guanshan Biota of eastern Yunnan, South China
- 2021
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Ingår i: Journal of Paleontology. - : Cambridge University Press. - 0022-3360 .- 1937-2337. ; 95:1, s. 40-55
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Tidskriftsartikel (refereegranskat)abstract
- Brachiopod shell accumulations are abundant and diverse in the lower Cambrian strata of Yunnan Province, South China, but most commonly they are composed of linguloid and acrotheloid brachiopods. Here, we describe the first record of shell beds with high-density accumulations of microscopic acrotretoid brachiopods (usually <2 mm in width) in the muddy deposits of the Wulongqing Formation (Guanshan Biota, Cambrian Stage 4) in the Wuding area of Yunnan Province. The acrotretoid shell beds from the Wulongqing Formation vary from thin mm-thick pavements to more well-developed beds, several centimeters thick. The occurrence of remarkably rich acrotretoid shell beds indicates that microscopic lingulates began to exert an important role in hardening and paving the soft-substrate seafloor during the early Cambrian evolution of Phanerozoic “mixgrounds.” The new Guanshan material is referred to a new species, Linnarssonia sapushanensis n. sp., which differs from other species of Linnarssonia mainly in having a well-developed internal pedicle tube, as well as a relatively longer dorsal median septum. The occurrence of Linnarssonia sapushanensis n. sp. in the Wulongqing Formation in eastern Yunnan extend the oldest record of the genus on the Yangtze Platform of South China back to at least Cambrian Stage 4.
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| 5. |
- Hu, Yazhou, et al.
(författare)
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First Report of Small Shelly Fossils from the Cambrian Miaolingian Limestones (Zhangxia and Hsuzhuang Formations) in Yiyang County, Henan Province of North China
- 2021
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Ingår i: Minerals. - : MDPI. - 2075-163X. ; 11:10
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Tidskriftsartikel (refereegranskat)abstract
- Small Shelly Fossils (SSFs) from the Cambrian are widely distributed and well known across different paleocontinents of the world. However, middle Cambrian SSFs from North China Platform have only rarely been documented until now. In this paper, we presented the first report on SSFs from bioclastic and oolitic limestones of the Zhangxia and Hsuzhuang formations of Henan province, North China. The carbonate-hosted fauna includes brachiopods (Micromitra sp., M. modesta, Eoobolus sp., and Schizopholis sp.), helcionellids (Oelandiellaaccordionata and O. aliciae), hyolithids, Hyolithellus sp., Chancelloriaeros, sponge spicules, echinoderm ossicles, and chancelloriid sclerites. In terms of preservation, the brachiopod shell valves of M. modesta appeared to be homogeneous, consisting of tightly packed phosphate grains. Eoobolus sp. is composed of primary layer and secondary baculate, both of which consist of tightly compacted phosphate grains. Schizopholis sp. has multiple-lamellar phosphatized microstructures that distinctly differ from the other brachiopods recovered from the Longwanggou section. A similar multiple-lamellar microstructure was also revealed in conchs of Hyolithellus, with tightly compacted phosphate grains. The argillaceous shell of Oelandiellaaccordionata and O. aliciae, and the calcitic inner molds of hyolith did not preserve any shell structure. The helcionellids O. accordionata and O. aliciae and the brachiopod M. modesta were reported for the first time from North China. The fauna is most similar to the middle Cambrian faunas of South Australia, in the brachiopod and mollusk components; it is also similar in composition of brachiopods and mollusks to coeval faunas from South China. The new fauna of SSFs in the Yiyang Longwanggou Section indicated that the Hsuzhuang and Zhangxia formations are late Drumian to middle Guzhuangian in age, most likely correlating with the Murrawong Creek Formation of South Australia.
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| 6. |
- Zhang, Zhifei, et al.
(författare)
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The oldest ‘Lingulellotreta’ (Lingulata, Brachiopoda) from China and its phylogenetic significance : integrating new material from the Cambrian Stage 3–4 Lagerstätten in eastern Yunnan, South China
- 2020
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Ingår i: Journal of Systematic Palaeontology. - : Taylor & Francis. - 1477-2019 .- 1478-0941. ; 18:11, s. 945-973
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Tidskriftsartikel (refereegranskat)abstract
- The origin of Cambrian brachiopods and their phylogenetic relationship with other lophotrochozoans is far from clear. Lingulellotretidae, the oldest family of lingulate brachiopods, is typified by possessing a pouch-like coelomic extension beyond the hinge line, subtended in a triangular pseudointerarea. The early Cambrian (Stage 4) linguloid brachiopod – originally described as ‘Lingulepis’ malongensis Rong, and later referred to Lingulellotreta within the Family Lingulellotretidae – is here redescribed and assigned to Eoobolus within the Family Eoobolidae, based on new exceptionally preserved topotype material from the type locality, part of the Guanshan Lagerstätte (Wulongqing Formation), Kunming–Malong area, eastern Yunnan, South China. For the first time, we provide a record of the soft anatomy, including a pedicle for the cosmopolitan genus Eoobolus. Due to loss of the type specimen, a neotype of E. malongensis is selected. Differing from the Guanshan E. malongensis, the Chengjiang species is slightly bigger in shell size, and possesses an elongated ventral pseudointerarea. In addition, new flattened specimens of ‘Lingulellotreta malongensis’ from the Chengjiang (Stage 3) biota, preserved in lateral and dorsoventral views, demonstrate an interior lophophore organization and a well-developed pedicle foramen, typical of the genus Lingulellotreta. When compared to the type species – Lingulellotreta ergalievi Koneva – from the Shabakty Group (Cambrian Stage 4), Malyi Karatau Range, Kazakhstan, the Chengjiang species possessed a more elongated ventral pseudointerarea, accommodating an extended body cavity, deepening posteriorly, with a recurved digestive tract. Accordingly, the Chengjiang specimens are thus referred to a new species, Lingulellotreta yuanshanensis sp. nov. The elongated, tubular extended body cavity of Lingulellotreta, which is not present in the slightly younger Guanshan Eoobolus, has recently gained further phylogenetic significance, as support continues to emerge for the view that a ‘tubular’ body plan may be primitive within the lophotrochozoans, notably brachiopods.
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