Surface of microorganisms

The classic pathway is triggered by the formation of factor Cl at IgG or IgM on the surface of microorganisms (left). Cl is an 18-part molecular complex with three different components (Clq, Clr, and Cls). Clq is shaped like a bunch of tulips, the flowers of which bind to the Fc region of antibodies (left). This activates Clr, a serine proteinase that initiates the cascade of the classic pathway. First, C4 is proteolytically activated into C4b, which in turn cleaves C2 into C2a and C2b. C4B and C2a together form C3 convertase [1], which finally catalyzes the cleavage of C3 into C3a and C3b. Small amounts of C3b also arise from non-enzymatic hydrolysis of C3. 

Another important defense tool of the immune system consists of specialized proteins called antibodies, or immunoglobulins, that are produced by lymphocytes and can recc nize and bind to proteins on the surfaces of microorganisms, resulting in their destruction and removal from the body. The disease-fighting lymphocytes that produce antibodies are able to remember previous exposure to a protein or other substance and respond quickly if it reappears in the body. Vaccination and other immunizations that prevent disease cause the immune system to develop the appropriate set of specific lymphocytes and antibodies that can quickly attack an infection. 

Georgiou, G., Stathopoulus, C., Daugherty, P. S., Nayak, A. R., Iverson, B. L., and Curtiss III, R. (1997). Display of heterologous proteins on the surface of microorganisms from the screening of combinatorial libraries to live recombinant vaccines. Nature Biotechnology, 15, 29-34. 

FIGURE 17.1 Schematic representation of a peptide display library. A pool of DNA fragments is synthesized, cloned into an appropriate vector, and expressed on the surface of microorganisms (e.g. bacteriophages). 

In order to express the peptides on the surface of microorganisms, the DNA is inserted into a gene coding for a coat or membrane protein, which is able to expose the peptide. Several such proteins are used. 

Vemadite on the surface of microorganisms may be part of a catalytic system in this oxidative biomineralization process. To clarify this point, a more detailed study of the oxidation kinetics of Mn(II) adsorbed to 8-Mn02 should complement the available data (1). 

Researchers have also used wet sample specimens in STXM to measure the NEXAFS spectra of bovine serum albumin and DNA (Ade et al. 1992 Fig. 11). These studies indicate that the C Is—>7t transitions of these samples are distinctly different with a greater signal for the CN moieties in DNA. Variations in these spectral features have been used to image the distribution of protein and DNA in cells (Fig. 11). This author has evaluated the variations in the C NEXAFS spectra of microorganisms to obtain a better understanding of their cell wall chemistry. His studies indicated that the surfaces of microorganisms exhibit distinct spectral differences when compared to that of the interior (SCB Myneni, unpublished results). 

FIGURE 1. Two distinct inodes of complement activation. Both the antibody-dependent (classical) and alternate pathways generate an enzyme-split fragment of C3 that binds to the surface of microorganisms which markedly potentiates phagocytosis. 

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