The AAX system from Chlamydia pneumoniae

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Title: The AAX system from Chlamydia pneumoniae
Author: Smith, Conor Blake
Abstract: Arginine uptake and degradation systems are common throughout bacteria and archaea . The genome of human pathogen Chlamydia pneumoniae encodes three proteins now called AaxA , AaxB , and AaxC which function together to take up arginine , decarboxylate it , and expel the decarboxylation product , agmatine . AaxB is the previously characterized pyruvoyl -dependent arginine decarboxylase , AaxC is an inner membrane amino acid transport protein that functions as an arginine -agmatine antiporter , and AaxA is an outer membrane porin , which facilitates the uptake of arginine and also functions as a general porin with broad specificity . C . pneumoniae is a non -typical Gram negative bacteria and an obligate intracellular parasite with a unique 2 -phase life cycle . The role of this system for arginine -agmatine exchange has yet to be determined but it may function to deplete host cell arginine as a means of inactivating host inducible nitric oxide synthase (iNOS ) , a molecule used in the innate immune response that has been shown to have an inhibitory affect on the growth of C . pneumoniae in cell culture . AaxB and AaxC are able to complement the loss of extreme acid -resistance in E . coli mutants that lack their own system for arginine -agmatine exchange , making pH homeostasis another possible role for this system . The porin AaxA is able to enhance arginine -agmatine exchange by AaxB and AaxC in E . coli mutants as well as by the native arginine decarboxylase AdiA and the native arginine -agmatine antiporter AdiC in wild type E . coli . AaxA is not an arginine -specific porin and instead acts as a general porin with a broad specificity . AaxA discriminates only against large and negatively charged solute molecules , and therefore it may have a broad role in the uptake of various biomolecules essential for chlamydial growth in addition to its role as part of a system for arginine -agmatine exchange .
URI: http : / /hdl .handle .net /2152 /ETD -UT -2009 -12 -482
Date: 2010-08-27

Citation

The AAX system from Chlamydia pneumoniae. Doctoral dissertation, The University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /ETD -UT -2009 -12 -482 .

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