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Please use this identifier to cite or link to this item: http://repository.li.mahidol.ac.th/dspace/handle/123456789/27673
Title: Characterization of -isopropylmalate synthases containing different copy numbers of tandem repeats in Mycobacterium tuberculosis
Authors: Wandee Yindeeyoungyeon
Supaporn Likitvivatanavong
Prasit Palittapongarnpim
Thailand National Center for Genetic Engineering and Biotechnology
Mahidol University
Keywords: Immunology and Microbiology;Medicine
Issue Date: 10-Aug-2009
Citation: BMC Microbiology. Vol.9, (2009)
Abstract: Alpha-isopropylmalate synthase (-IPMS) is the key enzyme that catalyzes the first committed step in the leucine biosynthetic pathway. The gene encoding -IPMS in Mycobacterium tuberculosis, leuA, is polymorphic due to the insertion of 57-bp repeat units referred to as Variable Number of Tandem Repeats (VNTR). The role of the VNTR found within the M. tuberculosis genome is unclear. To investigate the role of the VNTR in leuA, we compared two -IPMS proteins with different numbers of amino acid repeats, one with two copies and the other with 14 copies. We have cloned leuA with 14 copies of the repeat units into the pET15b expression vector with a His6-tag at the N-terminus, as was previously done for the leuA gene with two copies of the repeat units. Results. The recombinant His6 - IPMS proteins with two and 14 copies (-IPMS-2CR and -IPMS-14CR, respectively) of the repeat units were purified by immobilized metal ion affinity chromatography and gel filtration. Both enzymes were found to be dimers by gel filtration. Both enzymes work well at pH values of 78.5 and temperatures of 3742°C. However, -IPMS-14CR tolerates pH values and temperatures outside of this range better than -IPMS-2CR does. -IPMS-14CR has higher affinity than -IPMS-2CR for the two substrates, -ketoisovalerate and acetyl CoA. Furthermore, -IPMS-2CR was feedback inhibited by the end product l-leucine, whereas -IPMS-14CR was not. Conclusion. The differences in the kinetic properties and the l-leucine feedback inhibition between the two M. tuberculosis -IPMS proteins containing low and high numbers of VNTR indicate that a large VNTR insertion affects protein structure and function. Demonstration of l-leucine binding to -IPMS-14CR would confirm whether or not -IPMS-14CR responds to end-product feedback inhibition. © 2009 Yindeeyoungyeon et al; licensee BioMed Central Ltd.
URI: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=67651165639&origin=inward
http://repository.li.mahidol.ac.th/dspace/handle/123456789/27673
ISSN: 14712180
14712180
Appears in Collections:Scopus 2006-2010

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