The amino-terminal domain of the P-pilus adhesin determines receptor specificity

Pyelonephritic isolates of Escherichia coli commonly express P-pili, which mediate bacterial attachment to glycolipids on epithelial cell surfaces. Three classes of P-pili have been defined, based on varying specificity for galabiose-containing glycolipids. Variation in adhesive capacity is correlated with a shift in preferred host, suggesting that host tropism depends largely on detailed specificity for the globoseries glycolipids. In this study we examined the importance of the PapG adhesin in determining receptor specificity. Translational fusions were constructed between the ammo-terminus of the PapG adhesin from each of the three pilus classes and a reporter protein. The binding specificity of the purified fusion proteins in vitro was identical to that seen with whole bacteria. Adherence of intact bacteria to cultured kidney cells was markedly reduced by a monoclonal antibody specific for the Class III adhesin (previously denoted PrsG), confirming the importance of the ammo-terminus of PapG in mediating attachment to a receptor when presented on the eukaryotic cell surface. These results suggest that the detailed receptor specificity resides solely within the amino-terminus of the PapG adhesin and is independent of the complex pilus architecture.     

Glycine oxidation in mitochondria isolated from light grown and etiolated plant tissue

Mitochondria were isolated from light grown and dark grown monocotyledonous (wheat- Triticum aestivum and barley- Hordeum vulgare ) and dicotyledonous (pea- Pisum sativum ) plants and their capacity to oxidize glycine was measured. In all of the studied plant species the rate of mitochondrial glycine oxidation was high in light grown leaves. Glycine oxidation in mitochondria from etiolated leaves was also very substantial; the rate of glycine oxidation relative to the oxidation of other substrates was about half as compared to green tissue. In etiolated non-photosynthetic tissues the relative glycine oxidation was only ca 20% of that measured in green leaves. The effect of light on the development of glycine oxidation capacity was studied using etiolated barley which was transferred to light for 6 to 24 h. During this time the rate of glycine oxidation as compared to the oxidation of NADH and malate increased, approaching the ratio observed in light grown leaves. It is concluded that the synthesis of proteins involved in glycine oxidation is regulated both in a light dependent and in a tissue specific manner. Monocotyledonous plants should be very useful for further studies of this aspect due to the relatively small developmental difference between etiolated and light grown leaf tissue.