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The eukaryotic cytosolic Fe-S protein assembly (CIA) machinery inserts iron-sulfur (Fe-S) clusters into cytosolic and nuclear proteins. In the final maturation step, the Fe-S cluster is transferred to the apo-proteins by the CIA-targeting complex (CTC). However, the molecular recognition determinants of client proteins are unknown. We show that a conserved [LIM]-[DES]-[WF]-COO- tripeptide is present at the C-terminus of more than a quarter of clients or their adaptors. When present, this targeting complex recognition (TCR) motif is necessary and sufficient for binding to the CTC in vitro and for directing Fe-S cluster delivery in vivo. Remarkably, fusion of this TCR signal enables engineering of cluster maturation on a nonnative protein via recruitment of the CIA machinery. Our study advances our understanding of Fe-S protein maturation and paves the way for bioengineering novel pathways containing Fe-S enzymes. [ABSTRACT FROM AUTHOR]

The mass resolution of laser desorption ionization (LDI) single particle aerosol mass spectrometry (SPAMS) is usually low (~500), which has been greatly improved by recent development of delayed ion extraction technique. However, due to large fluctuations among LDI processes during each laser shot, accurate calibration of mass-to-charge ratio for high resolution SPAMS spectra is challenging. Here we developed an automatic linear calibration method to improve the accuracy of mass-to-charge (m/z) measurement for single atmospheric aerosol particles. Laboratory generated sea spray aerosol and atmospheric ambient aerosol were tested. After the calibration, the fluctuation ranges of the reference ions (e.g. Pb+ and SO4+) m/z reaches ±0.018 for sea spray aerosol and ±0.024 for ambient aerosol in average mass spectra. With such m/z accuracy, the HR-SPAMS spectra of sea spray aerosol can easily identify elemental compositions of organic peaks, such as Cx, CxHy and CxHyOz. While the chemical compositions of ambient aerosols are more complicated, CxHy, CxHyOz and CNO peaks can also be identified based on their accurate mass. With the improved resolution, the time series of peaks with small m/z differences can be separated and measured. In addition, it is also found that applying high resolution data with enhanced mass calibration can significantly affect particle classification (identification) using the ART-2a algorism, which classify particles based on similarities among single particle mass spectra. [ABSTRACT FROM AUTHOR]