title: New insights into the function of the iron deficiency-induced protein C from Synechococcus elongatus PCC 7942.
abstract: Iron limitation has a strong impact on electron transport reactions of the unicellular fresh water cyanobacterium Synechococcus elongatus PCC 7942 (thereafter referred to as S. elongatus). Among the various adaptational processes on different cellular levels, iron limitation induces a strongly enhanced expression of IdiC (iron-deficiency-induced protein C). In this article, we show that IdiC is loosely attached to the thylakoid and to the cytoplasmic membranes and that its expression is enhanced during conditions of iron starvation and during the late growth phase. The intracellular IdiC level was even more increased when additional iron was replenished in the late growth phase. On the basis of its amino acid sequence and of its absorbance spectrum, IdiC can be classified as a member of the family of thioredoxin (TRX)-like (2Fe-2S) ferredoxins. The presence of an iron cofactor in IdiC was detected by inductive coupled plasma optical emission spectrometry (ICP-OES). Comparative measurements of electron transport activities of S. elongatus wild type (WT) and an IdiC-merodiploid mutant called MuD, which contained a strongly reduced IdiC content under iron-sufficient as well as iron-deficient growth conditions, were performed. The results revealed that MuD had a strongly increased light sensitivity, especially under iron limitation. The measurements of photosystem II (PS II)-mediated electron transport rates in WT and MuD strain showed that PS II activity was significantly lower in MuD than in the WT strain. Moreover, P(700) (+) re-reduction rates provided evidence that the respiratory activities, which were very low in the MuD strain in the presence of iron, significantly increased in iron-starved cells. Thus, an increase in respiration may compensate for the drastic decrease of photosynthetic electron transport activity in MuD grown under iron starvation. Based on the similarity of the S. elongatus IdiC to the NuoE subunit of the NDH-1 complex in Escherichia coli, it is likely that IdiC has a function in the electron transport processes from NAD(P)H to the plastoquinone pool. This is in agreement with the up-regulation of IdiC in the late growth phase as well as under stress conditions when PS II is damaged. As absence or high reduction of the IdiC level would prevent or reduce the formation of functional NDH-1 complexes, under such conditions electron transport routes via alternative substrate dehydrogenases, donating electrons to the plastoquinone pool, can be assumed to be up-regulated.
authors: Lehrstuhl für Molekulare Zellphysiologie, Fakultät für Biologie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany.
authors: Daniel
authors: D
authors: Pietsch
authors: Gábor
authors: G
authors: Bernát
authors: Uwe
authors: U
authors: Kahmann
authors: Dorothee
authors: D
authors: Staiger
authors: Elfriede K
authors: EK
authors: Pistorius
authors: Klaus-Peter
authors: KP
authors: Michel
references: J Bacteriol. 2000 Feb;182(3):714-22
references: 10633105
references: Nature. 1970 Aug 15;227(5259):680-5
references: 5432063
references: Z Naturforsch C J Biosci. 2000 Nov-Dec;55(11-12):927-42
references: 11204198
references: Plant Physiol. 2006 Apr;140(4):1451-63
references: 16489137
references: Biochemistry. 2002 Mar 12;41(10):3422-9
references: 11876651
references: J Biol Chem. 2003 Oct 17;278(42):41093-8
references: 12882966
references: Biochim Biophys Acta. 2007 Jun;1767(6):528-34
references: 17316552
references: J Bacteriol. 2001 Jul;183(14):4251-8
references: 11418566
references: FEBS Lett. 2000 Aug 11;479(1-2):1-5
references: 10940377
references: J Biol Chem. 2008 May 2;283(18):12520-7
references: 18252722
references: J Biol Chem. 2007 Sep 14;282(37):27468-27477
references: 17626019
references: Z Naturforsch C J Biosci. 2007 Mar-Apr;62(3-4):273-84
references: 17542496
references: Biochim Biophys Acta. 1980 Feb 14;611(2):227-40
references: 6766743
references: Plant Physiol. 1983 Nov;73(3):724-8
references: 16663290
references: J Am Chem Soc. 2009 May 6;131(17):6149-53
references: 19366265
references: J Bacteriol. 2000 Nov;182(22):6523-4
references: 11053401
references: Arch Microbiol. 2003 Dec;180(6):471-83
references: 14605795
references: J Biol Chem. 2005 Feb 18;280(7):5820-7
references: 15576371
references: Biochemistry. 1982 Jul 6;21(14):3294-8
references: 7115670
references: Eur J Biochem. 2000 Oct;267(19):5900-7
references: 10998049
references: Photosynth Res. 2007 Oct;94(1):91-108
references: 17690995
references: J Exp Bot. 2009;60(3):1035-46
references: 19213808
references: Biochemistry. 1993 Aug 17;32(32):8251-8
references: 8394132
references: FEBS Lett. 1993 Jul 12;326(1-3):246-50
references: 8325373
references: J Biol Chem. 2005 Mar 11;280(10):9283-90
references: 15613474
references: J Bacteriol. 2011 Jan;193(1):292-5
references: 21036997
references: Plant Cell Physiol. 2001 Aug;42(8):823-7
references: 11522907
references: Biochim Biophys Acta. 2011 Aug;1807(8):935-44
references: 21035426
references: Microbiology (Reading). 1997 Nov;143 ( Pt 11):3543-3553
references: 9387233
references: Physiol Plant. 2004 Jan;120(1):36-50
references: 15032875
references: J Bacteriol. 2001 May;183(9):2779-84
references: 11292796
references: Plant Physiol. 1993 Sep;103(1):171-180
references: 12231924
references: Microbiology (Reading). 1999 Jun;145 ( Pt 6):1473-1484
references: 10411274
references: J Theor Biol. 1997 Aug 21;187(4):529-40
references: 9299297
references: Microbiology (Reading). 2002 Oct;148(Pt 10):3293-3305
references: 12368463
references: Plant Physiol. 2008 Jun;147(2):747-63
references: 18424627
references: Microbiology (Reading). 1998 Dec;144 ( Pt 12):3425-3436
references: 9884235
references: Photosynth Res. 1985 Sep;6(3):261-71
references: 24442924
references: J Biol Chem. 2009 Oct 9;284(41):27875-27883
references: 19674969
references: Physiol Plant. 2002 Oct;116(2):255-263
references: 12354203
references: Photosynth Res. 2009 Mar;99(3):205-16
references: 19137411
references: Microbiology (Reading). 1996 Sep;142 ( Pt 9):2635-45
references: 8828233
references: J Bacteriol. 2001 Sep;183(17):5015-24
references: 11489854