Import inhibition of poly(His) containing chloroplast precursor proteins by Ni2+ ions.
The precursor of the small subunit of ribulose-1,5-bisphosphate carboxylase (pSS) and a modified pSS containing a C-terminal hexahistidyl tail (pSS(His)6) were imported into isolated Chlamydomonas chloroplasts with comparable efficiency. In the presence of Ni2+ ions the import of pSS(His)6 was inhibited and the precursor bound to the envelope remained protease sensitive, while import of pSS was not affected. Addition of an excess of L-histidine suppressed the inhibition demonstrating that the hexahistidyl-Ni2+ complex was responsible for import inhibition. Inhibition could be observed between about 0.5 and 10 mM Ni2+, depending on the total protein content in the assay. Import incompetent Ni2+ -precursor complexes can be used to study early events in chloroplast protein import.
Rothen
R
R
Institut für Biochemie, Universität Bern, Switzerland.
Thiess
M
M
Schumann
P
P
Boschetti
A
A
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002696:Chlamydomonas / Q000187:drug effects / Q000378:metabolism; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D006639:Histidine / Q000737:chemistry / Q000235:genetics; D009532:Nickel / Q000494:pharmacology*; D011498:Protein Precursors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*
D011498:Protein Precursors; D011993:Recombinant Fusion Proteins; D006639:Histidine; D009532:Nickel; D012273:Ribulose-Bisphosphate Carboxylase