sll0617 encodes a cyanobacterial VIPP1 homologue, and it
seems to be located exclusively in the plasma membrane.
(a) Immunoblotting with α-VIPP1 and α-PspA antisera
identifies VIPP1 in Synechocystis. Lanes 1–3,
immunoblot performed with α-VIPP1; lanes 4–6, immunoblot performed
with α-PspA; lanes 1 and 4, total leaf extract from A.
thaliana; lanes 2 and 5, total protein extract from
Synechocystis; lanes 3 and 6, PspA, heterologously
expressed in and purified from E. coli.
(b) Synechocystis wild-type cells were
separated into outer membrane (OM), plasma membrane (PM), cytoplasm
(SOL), and thylakoids (THY). Each fraction was analyzed by
immunoblotting for the presence of VIPP1. Antisera against the 75-kDa
outer membrane protein (α-syn-Toc75), large subunit of Rubisco
(α-RbcL), ATP synthase (α-AtpA/B), and nitrate reductase subunit
A (α-NrtA) were used as markers for the purity of the different
subfractions. (c) sll0617 was disrupted
by the insertion of a kanamycin-resistance cassette at position 454 of
the coding region. (d) Southern blot analysis was
carried out with wild-type and Δsynvipp1 genomic DNA
to confirm the disruption of sll0617. (e)
Immunoblotting with α-VIPP1 protein establishes an extreme reduction
of the level of VIPP1 protein in the Δsynvipp1 mutant
compared with wild-type and rescue cells.