Integrating structure-based machine learning and co-evolution to investigate specificity in plant sesquiterpene synthases

Sesquiterpene synthases (STSs) catalyze the formation of a large class of plant volatiles called sesquiterpenes. While thousands of putative STS sequences from diverse plant species are available, only a small number of them have been functionally characterized. Sequence identity-based screening for desired enzymes, often used in biotechnological applications, is difficult to apply here as STS sequence similarity is strongly affected by species. This calls for more sophisticated computational methods for functionality prediction. We investigate the specificity of precursor cation formation in these elusive enzymes. By inspecting multi-product STSs, we demonstrate that STSs have a strong selectivity towards one precursor cation. We use a machine learning approach combining sequence and structure information to accurately predict precursor cation specificity for STSs across all plant species. We combine this with a co-evolutionary analysis on the wealth of uncharacterized putative STS sequences, to pinpoint residues and distant functional contacts influencing cation formation and reaction pathway selection. These structural factors can be used to predict and engineer enzymes with specific functions, as we demonstrate by predicting and characterizing two novel STSs from Citrus bergamia.     

Epileptische Enzephalopathie und Zahnschmelzdefekt (Kohlschütter-Tönz-Syndrom)

Kohlschütter-Tönz syndrome is a rare genetic disorder with neurologic symptoms – epilepsy and severe developmental delay – and defective enamel leading to yellow or brownish discoloration of teeth. The first family was described in 1974, all affected patients were male. In the meantime, families with both male and female patients were identified as well. Inheritance is thus most probably autosomal recessive; genetic heterogeneity can however not be ruled out. Clinical course and disease severity may differ even within one family. As the genetic basis has not yet been elucidated, diagnosis must be made on clinical grounds. We report three new children with Kohlschütter-Tönz syndrome in comparison to the 21 hitherto published cases.     

Immunotherapy of a murine ovarian carcinoma with Corynebacterium parvum and specific heteroantiserum. I. Activation of peritoneal cells to mediate antibody-dependent cytotoxicity.

Immunotherapy with a combination of Corynebacterium parvum and specific heteroantiserum is significantly more effective than treatment with either single agent in prolonging the survival of mice that have recevied an i.p. injection of syngeneic murine ovarian carcinoma (MOT) cells. Invitro, a combination of C. parvum-activated peritoneal cells and specific heteroantiserum has proven significantly more effective than either single component in destroying 51Cr-labeled MOT cells in the absence of complement. Activation of peritoneal cells to produce lysis of tumor in the presence specific antiserum peaked 3 to 7 days after a single injection of C. parvum and declined to baseline over 3 to 4 weeks. With repeated i.p. injections of C. parvum at appropriate intervals, activation of peritoneal cells could be prolonged and augmented. Among the routes tested, only i.p. administration of C. parvum was effective, although activation of peritoneal cells for cooperation with heteroantiserum was observed over a broad range of i.p. dosage (0.45 to 4.20 mg). These data suggest that the administration of C. parvum by appropriate doses, routes, and schedules can attract and activate a population of peritoneal effectors that mediate antibody-dependent cytotoxicity more effectively than resident peritoneal cells.     

Constitutive Production of Macrophage Colony-Stimulating Factor and Interleukin-6 by Human Ovarian Surface Epithelial Cells

Normal and neoplastic epithelial cells produce growth factors that can affect cells from different lineages. Epithelial ovarian cancers produce M-CSF and IL-6. In the present study, production of these cytokines has been measured in the apparently normal epithelial cells from which epithelial ovarian neoplasms are thought to arise. Epithelial cells from the surface of premenopausal human ovaries were established in short-term cultures. The cells bound anti-cytokeratin antibodies and exhibited characteristic epithelial morphology by light and transmission electron microscopy. M-CSF and IL-6 were detected in supernatants from cultures of these cells, using assays specific for each factor. Cytokine levels were comparable to those in supernatants from ovarian and breast cancer cell lines. M-CSF expression could also be demonstrated by immunohistochemical analysis with specific rabbit heteroantiserum. Thus, M-CSF and IL-6 are produced constitutively by normal as well as by neoplastic ovarian epithelium.