Protein Import into and Sorting inside the Chloroplast Are Independent Processes.

Plastocyanin is a nuclear-encoded chloroplast thylakoid lumen protein that is synthesized in the cytoplasm with a large N-terminal extension (66 amino acids). Transport of plastocyanin involves two steps: import across the chloroplast envelope into the stroma, followed by transfer across the thylakoid membrane into the lumen. During transport the N-terminal extension is removed in two parts by two different processing proteases. In this study we examined the functions of the two cleaved parts, C1 and C2, in the transport pathway of plastocyanin. The results show that C1 mediates import into the chloroplast. C1 is sufficient to direct chloroplast import of mutant proteins that lack C2. It is also sufficient to direct import of a nonplastid protein and can be replaced functionally by the transit peptide of an imported stromal protein. C2 is a prerequisite for intraorganellar routing but is not required for chloroplast import. Deletions in C2 result in accumulation of intermediates in the stroma or on the outside of the thylakoids. The fact that C1 is functionally equivalent to a stromal-targeting transit peptide shows that plastocyanin is imported into the chloroplast by way of the same mechanism as stromal proteins, and that import into and routing inside the chloroplasts are independent processes.

Prevalence of drug-drug interactions in the era of HIV integrase inhibitors: a retrospective clinical study.

BACKGROUND: Antiretroviral agents pose a high risk for drug-drug interactions (DDIs), mainly but not limited to being a substrate, inducer or inhibitor of P450 cytochrome enzymes. In part metabolised by other pathways, integrase inhibitors might show a more favourable profile. The aim of this study was to investigate the prevalence of DDIs in daily clinical practice for patients starting different antiretroviral treatment (ART) regimens. METHODS: All patients starting ART in our centre from January 2009 to April 2016 were included. All prescribed co-medications since the start of ART were recorded retrospectively from the medical files and screened for DDIs using the Liverpool HIV drug interaction database. Only DDIs between antiretroviral and non-antiretroviral drugs were considered. RESULTS: We included 145 patients, of which 42% were on an integrase inhibitor-based regimen, mainly dolutegravir and elvitegravir. Of the patients, 78% (n = 113) took co-medication. Potential DDIs were seen in 63% of the patients with co-medication; contraindicated prescriptions were detected in 1%. Protease inhibitor-based ART was a risk factor for DDI (odds ratio (OR) 2.57; 95% confidence interval (CI) 1.06-6.19), in contrast to non-nucleoside reverse transcriptase inhibitor-based ART (OR 0.77; 95% CI 0.32-1.84). Concerning integrase inhibitors, a significantly lower risk was seen with dolutegravir-based treatment (OR 0.35; 95% CI 0.15-0.82), though not for elvitegravir-based ART (OR 2.51; 95% CI 0.66-9.58). CONCLUSIONS: ART regimens pose a dissimilar risk for drug-drug interactions in clinical practice. Regarding the use of integrase inhibitors, a significantly lower risk was seen with dolutegravir-based treatment.