Naslov
Import characterization of a chloroplastic intermembrane space protein

Autori
Vojta, Lea ; Bölter, Bettina ; Soll Jürgen

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Zbornik sažetaka 9. Hrvatskog biološkog kongresa / Besendorfer, Višnja ; Klobučar, Göran I.V. - Zagreb : Hrvatsko biološko društvo, 2006, 107-109

ISBN
953-6241-06-4

Skup
9. hrvatski biološki kongres s međunarodnim sudjelovanjem

Mjesto i datum
Rovinj, Hrvatska, 23.09.2006. - 29.09.2006

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
Import; chloroplasts; intermembrane space; Tic22

Sažetak
Less than 200 proteins needed for chloroplast development and proper function are encoded by the chloroplastic genome and synthesized in the stroma. Around 3000 other genes had been transferred to the nucleus in the course of evolution, where they acquired targeting signals for import back into the organelle. Dependent on their fi nal location, proteins destined for chloroplasts can insert either spontaneously, like most of outer envelope proteins, target to the stroma and subsequently re-export to the inner envelope membrane, or insert into the inner envelope directly, by stop-transfer signal. Proteins targeted to thylakoids mostly contain a bipartite presequence, which targets them fi rst to the stroma, while its second part determines the pathway for the thylakoids. The pathway for targeting to the intermembrane space of chloroplasts has not been intensively studied yet. For this reason, the analysis of the translocation of a 22 kDa intermembrane space localized protein was issued. It is a nuclear-encoded protein, synthesized on cytosolic ribosomes with a cleavable N-terminal chloroplast targeting presequence. It is found to be associated with the outer face of the inner envelope membrane, as well as with the inner face of the outer envelope, even though at a lower level. We confi rmed that import of Tic22 is enhanced by, but not dependent on, addition of external ATP and that it demands thermolysin sensitive components on the chloroplast surface. By chemical crosslinking and immunoprecipitation we have demonstrated that Tic22 interacts with components of the Toc translocon of the chloroplast outer envelope during its translocation. By performing import competition experiments we proved that Tic22 uses Toc machinery of the general import pathway. Therefore, proteins targeted to the intermembrane space seem to use the same translocation mode as stromal proteins.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

POVEZANOST RADA