T. Matsumura et al., Complementary DNA cloning and characterization of ferredoxin localized in bundle-sheath cells of maize leaves, PLANT PHYSL, 119(2), 1999, pp. 481-488
In maize (Zea mays L.) two leaf-specific ferredoxin (Fd) isoproteins, Fd I
and Fd II, are distributed differentially in mesophyll and bundle-sheath ce
lls. A novel cDNA encoding the precursor of Fd II (pFD2) was isolated by he
terologous hybridization using a cDNA for Fd I (pFD1) as a probe. The assig
nment of the cDNAs to the Fds was verified by capillary liquid-chromatograp
hy/electrospray ionization-mass spectrometry. RNA-blot analysis demonstrate
d that transcripts for Fd I and Fd II accumulated specifically in mesophyll
and bundle-sheath cells, respectively. The mature regions of pFD1 and pFD2
were expressed in Escherichia coli as functional Fds. Fd I and Fd II had s
imilar redox potentials of -423 and -406 mV, respectively, but the K-m valu
e of Fd-NADP(+) reductase for Fd II was about 3-fold larger than that for F
d I. Asparagine at position 65 of Fd II is a unique residue compared with F
d I and other Fds from various plants, which have aspartic acid or glutamic
acid at the corresponding position as an electrostatic interaction site wi
th Fd-NADP(+) reductase. Substitution of asparagine-65 with aspartic acid i
ncreased the affinity of Fd II with Fd-NADP(+) reductase to a level compara
ble to that of Fd I. These structural and functional differences of Fd I an
d Fd II may be related to their cell-specific expression in the leaves of a
C-4 plant.