news
RESEARCH PROFILES
“Broadband” proteomics tackles TB
of the five lipid metabolism proteins encoded by the kas operon, which are Tuberculosis (TB) is responsible for an likely targets of INH, were identified in estimated 2 million deaths a nnually these experiments, whereas previous and is increasingly becoming multiproteomic analyses with 2DE/MS have drug resistant (MDR). Development only identified two. A large number of of new treatments for TB is crucial: Alconserved hypothetical proteins were though effective first-line drugs are in the proteome, several of which were available, the mortality rate for a perdifferentially expressed in control and son who develops MDR TB is equivaINH-exposed bacteria. lent to that for someone who goes withThis study has left a wealth of inout treatment. To this end, researchers formation in its wake—and a wealth are striving for a more complete underof possibilities in its future. “One sees standing of the TB proteome and how it the direct effect on lipid metabolism, is influenced by current drugs. but also a number of other celIn this issue of JPR (pp 54– lular responses are evident,” 63), researchers report on a new Townsend says. This means LC/MS-based technique that that instead of a clear experihas been put to the test against ment pointing only to the preMycobacterium bovis BCG and cise target of drug action, one a common TB drug, isoniaalso sees a cell coping with imzid (INH). The proteomes have minent death. Looking ahead, come in—as highly complex, acTownsend sees time-course curate data about the sequence studies as one way to improve on and quantitative comparisons of the technique: One could look at nearly 6700 peptides. “Data acthe proteome within minutes of quisition using this low/high INH exposure as well as further strategy,” says Jeff Silva of Waters down the line. This approach Corp., one of the study’s authors, should be possible as soon as A comprehensive look. Time-resolved LCMS E mass measurements of precursor (blue) and fragment (red) ions. “is like using a broadband Interdata-handling capabilities grow net connection versus a dial-up more sophisticated. And he’s modem connection. We obtain looking forward to using LCMSE precursor and fragment information for we have parallel fragmentation data to investigate the cellular effects and all the peptides eluting from the LC colthat tells us what the sequence of the define the primary target of a new poumn at every moment, as opposed to peptide is,” he explains. “Now, when we tential drug, discovered at Johns Hopthe serial nature of previous mass specrun two different experiments, we can kins, for TB chemotherapy. trometry approaches.” actually compare peptides from one exSilva and his colleagues at Waters Craig Townsend and Minerva periment to another experiment behave a number of ongoing collaboraHughes at Johns Hopkins University cause we have that level of specificity tions that use their LCMSE method for collaborated with Silva and his Waters down to the sequence.” microbial, parasitic, and human procolleagues, who had reported their deTownsend and colleagues compared teome analyses. “There’s not much velopment of this “broadband” LCMSE control lysates of M. bovis with INH-excoming out about antimicrobials and protein identification and quantitation posed lysates. A total of 6699 matched not much known about good antivimethod in the April 1, 2005, issue of Anpeptide components were found in the rals,” says Silva, “and these are bioalytical Chemistry (pp 2187–2200). The proteome analysis, and 103 proteins logical systems that are very ripe for method uses rapid cycling of a mass were identified with confidence from the picking for this type of technolospectrometer between low- and high956 peptides. Twenty-four of the 103 gy.” Proteomic analyses of virulent and energy channels. identified proteins were differentially nonvirulent strains of the same miINH, a cell-wall biosynthesis inhibiexpressed between control and INH-excrobe or drug-resistant and nonresistor, and M. bovis constitute an ideal sysposed bacteria. The authors assert that tant bacteria, says Silva, could identitem in which to try out LCMSE : wellthe differential expression observed in fy proteins that convey that virulence characterized enough to allow results the study supports the previously charor drug resistance and lead to more tarto be cross-validated, yet actively reacterized biochemical effects of mycogeted, rational drug design. searched because INH’s exact mechbacteria after INH exposure. Four out —Amy Hodson Thompson
© 2006 American Chemical Society
anism is still sought. Townsend and colleagues grew M. bovis in culture, exposed the bacteria to INH for 6 h, then harvested the proteins and analyzed them using LCMSE. Because LCMSE collects comprehensive and concise data, the method is amenable to label-free quantitative methods, and the protein lysates are subjected to minimal processing before they are analyzed, says Silva. “The information that we collect has both the accurate precursor peptide mass measurement, typically below 5 ppm, and
Journal of Proteome Research • Vol. 5, No. 1, 2006 13
