Chorion proteins

Figure 39-18. Schematic representation of the amplification of chorion protein genes s36 and s38. (Reproduced, with permission, from Chisholm R Gene amplification during development. Trends Biochem Sci 1982,7 161.)...

A particularly well studied example of functional amyloid is provided by Curli assembly (53). Curli amyloids are assembled by bacteria such as Escherichia coli and Salmonella. Once assembled on the extracellular surface, Curli amyloid fibers function as natural ceU adhesion molecules that link together bacterial cells into robust cellular networks of biofilms. Other examples of functional amyloids include the silk fibers observed commonly in spider webs the Chorion proteins of egg shells Factor XII, which is an activator of the hemostatic system and other naturally produced adhesives and materials (54). 

Insects and arachnoids produce well-known amyloids. Silk and spider webs, like P-keratin, also differ from amyloids in being fibrous P-sheet proteins composed of peptide strands that are parallel, rather than perpendicular, to the direction of the fibril axis. For the process of silk formation by spiders, it has been proposed that fibrils in the silk gland have an initial cross-P structure (Kenney et al. 2002 Table 3) that, when stretched, assume parallel P-structures. However, X-ray diffraction for a peptide derived from the central domain of the A class of chorion proteins, derived frovaAntheraea polyphemus eggshells, displayed P-sheets perpendicular to the fibril axis, the same cross-P structure that occurs in amyloid proteins (Iconomidou et al. 2000 Table 3). The stability and strength of the amyloid fibres provides mechanical and biological protection for the oocyte and developing embryo from a variety of environmental and predatory hazards. 

Hamodrakas SJ, Hoenger A, Iconomidou VA (2004) Amyloid fibrillogenesis of silkmoth chorion protein peptide-analogues via a liquid-crystalhne intermediate phase. J Struct Biol 145 226-235... 

Chorionic gonadotropin (CG) is produced in the placenta. Together- with the pituitary hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), it constitutes the glycoprotein family of gonadotropins. The actions of CG are mediated by the LH receptor, both belonging to the superfamily of G-protein Coupled Receptors. 

A.F. Chetcuti, D.K.Y. Wong, and M.C. Stuart, An indirect perfluorosulfonated ionomer-coated electrochemical immunosensor for the detection of the protein human chorionic gonadotrophin. Anal. Chem. 71, 4088-4094 (1999). 

Wu, H., et al. (1994). Structure of human chorionic gonadotropin at 2.6 A resolution from MAD analysis of the selenomethionyl protein. Structure 2, 545-558. 

Amplification of DNA of chromosomes. During formation of oocytes parts of the DNA are "amplified" by repeated replication. This provides a way for the ovum to accumulate ribosomal RNA and various proteins in large amounts. Similarly, genes for two abundant proteins of the egg shell or chorion of insects are amplified. Bidirectional replication initiated at discrete positions yields an "onion skin" structure containing many copies of an 90-kb sequence containing the two genes. The polyploidy observed in some highly specialized cells such as the Purkinje cells... 

Resistance of activated protein C and deep calf vein thrombosis has been reported during controlled ovarian stimulation for in vitro fertilization (18). The thrombosis occurred on the eighth day of human menopausal gonadotropin use and before human chorionic gonadotropin was given. 

Along this line Matsue et al. [37,45,78,79] have developed a number of biochips. Among them are multi-analyte assays for human placental lactogen (HPL) and human chorionic gonadotropin (HCG) [45] and leukocidin, a toxic protein produced by methicillin-resistant Staphylococcus aureus [79]. Figure 37.8 shows an example of a dual immunoassay with SECM detection. The analyte is defined by the position on the chip and the amount of analyte is quantified via the collection current at the UME. The current originates from the reduction of ferrocinium methanol (Fc+) at the UME. Fc+ is produced locally at the chip surface by the enzyme HRP under consumption of H202. 

Kohen P, Castro O, Palomino A, et al. The steroidogenic response and corpus luteum expression of the steroidogenic acute regulatory protein after human chorionic gonadotropin administration at different times in the human luteal phase. J Clin Endocrinol Metab. 2003 88 3421-3430. 

The gonatropins are a family of hormones that include follicle stimulating hormone (FSH), luteinizing hormone (LH), and chorionic gonadotropin (CG), among others. These three proteins are heterodimers that contain an identical polypeptide subunit (a) and another specific subunit ( 3), which confer the respective biological activity. FSH has a molar mass of 34 kDa, 14% of it being due to carbohydrate side chains. LH has a molar mass of 28.5 kDa. 

Abbreviations and trivial names used are RME, receptor-mediated endocytosis LDL, low density lipoprotein EGF. epidermal growth factor SDS, sodium dodecyl sulfate LH, luteinizing hormone hCG, human chorionic gonadotropin and G protein, guanine nucleotide binding protein. 

Prenatal diagnosis of I-cell disease has been based on greatly reduced phosphotransferase activity (cf. Biochemical Perspectives section) and abnormal intracellular-extracellular distribution of lysosomal enzymes in cultured amni-otic fluid cells (Table 17-3).As indicated in Table 17-3, amniotic fluid cells secrete large amounts of lysosomal enzymes into the extracellular medium. Decreased levels of lysosomal enzymes in chorionic villi obtained by biopsy have also been observed in I-cell disease however, the characteristic secondary effect (i.e.,increased levels of lysosomal enzymes in the extracellular compartment) is only partially expressed or not expressed at all in chorionic villi, suggesting an alternative mechanism for the transport of lysosomal proteins. Although... 

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