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Interactions between the light-harvesting subunits
and the non-covalently bound photopigments attribute considerably to the
spectral properties of photosynthetic bacteria light-harvesting complexes. In
our previous studies, we have constructed a novel Rhodobacter sphaeroides expression system. In the present study,
we focus on the spectral properties of LH2 when heterologously express LH2 with β-subunit- GFP fusion protein in Rb. sphaeroides. Near infra-red
spectrum of LH2 remained nearly unchanged as measured by spectroscopy.
Fluorescence spectrum suggested that the LH2 with β-subunit-GFP fusion protein complexes still possessed normal
activity in energy transfer. However, photopigments contents were
significantly decreased to a very low level in the LH2
with β-subunit-GFP fusion protein
complexes compared to that of LH2. FT-IR spectra indicated that interactions
between photopigments and LH2 α/β- subunits appeared not to be changed.
It was concluded that the LH2 spectral properties exhibited very similar even
when heterologously expressed LH2 b-subunit
fusion protein in Rb. sphaeroides.
Our present study may supply a new insight into better understand the interactions
between light-harvesting subunits and photopigments and bacterial photosynthesis
and promote the development of the novel Rb.
sphaeroides expression system.
Antibiotic resistant Escherichia coli strains are becoming more common recently. OmpA
is a very important antigen protein of E.
coli, which consists of two separate domains, N-terminal and C-terminal
domain. The N-terminal domain contains eight β- barrel regions that plays important roles in the multifaceted
functions of OmpA. In the present study, we cloned a mutant OmpA gene from a
multi-antibiotic resistant E. coli strain. Sequence analysis indicated that the N-terminal DNA sequence of the
mutant OmpA shared 81.05% homology with the modeled OmpA from E. coli K12 and the N-terminal amino
acid sequence of the mutant OmpA was 81.22% identical to that of the E. coli K12 OmpA. Moreover, several
amino acids located in the β-barrel
region were mutated. The mutant OmpA was expressed in BL21 suggested by
SDS-PAGE. Resistance to environmental stress assay indicated that the
N-terminus mutant OmpA still possessed excellent activities in pH, temperature
and osmotic pressure resistance. Our pre- sent study may supply insights into
better and deeper understand the relationships between OmpA N-terminal
regions and its functions in environmental stress conditions and the mechanisms
on antibiotic resistance of E. coli.