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M. Rashid et al.
found in the outer membrane of the gram-negative bacteria. The outer membrane
is asymmetrical and has LPS as one of the layers as shown in Fig. 27c. The
machinery involved in insertion of these proteins in outer membrane is called the
β-barrel assembly machinery (BAM) [91]. BAM complex’s structure and functional
details were elucidated within the membrane using high resolution ssNMR spectroscopy [92]. The outer membrane protein AIL from Yersinia pestis, a key component in the infection process which interacts with human protein vitronectin, has
been shown to interact with LPS present in outer membrane [78, 93]. Similarly
the structure of a 32 kDa β-barrel integral membrane protein from human; voltage
dependent anion channel (VDAC, controlling the ion transport across the outer
mitochondrial membrane) and its interaction with lipid membranes Dipalmitoylphosphatidyl-choline (DMPC) has been studied in liposomes and lipid crystals
[94].
9.3.2 Membrane Protein Structure and Function by Solution NMR
Solution NMR membrane protein samples include micelles, isotropic bicelles, and
nanodiscs, some of them are shown in Fig. 27. The proteins inserted in these
membrane models reorient rapidly hence they are in solution NMR dynamics range.
Micelles are formed from detergents and normally the signal intensity is very good
and resolution is better, however detergents interact with proteins and in due course
of time nanodiscs started to become very popular as membrane model for solution
NMR of proteins [95–97]. In nanodiscs the sized of the lipid discs are controlled by
membrane scaffold proteins (MSPs). Different sizes of the discs can be prepared by
changing the size of MSPs [98, 99]. Nanodisc model were popularized in solution
NMR of membrane proteins by Wagner group [100]. The structure of AIL has been
solved in nanodiscs also [78].
It has been shown that LPS in outer membrane of Yersinia pestis interacts with
AIL and co-operates in infection process. This was proved recently by Singh et al.,
that nanodiscs can be prepared where LPS can be inserted inside nanodisc (Fig. 27e)
[101] and it can provide us the details of the interaction of AIL with LPS [77].
The residues of AIL near the membrane and the side chains from His side chain
interacts with LPS. This interaction effectively thickens the membrane and helps
the bacterium to evade the immune system [102]. Another progress was studying
Cytp450, a family of enzymes involved in the catalysis of wide range of substrates.
Cytp450 and its redox partner cytochrome b 5 (cytb 5 ) were reconstituted within a
single nanodisc to study the functional process using NMR spectroscopy [103]. A
recent progress in this area which is subject of active research these day is to replace
MSPs with polymers to prepare more stable and useful nanodisc [104].
M. Rashid et al.
found in the outer membrane of the gram-negative bacteria. The outer membrane
is asymmetrical and has LPS as one of the layers as shown in Fig. 27c. The
machinery involved in insertion of these proteins in outer membrane is called the
β-barrel assembly machinery (BAM) [91]. BAM complex’s structure and functional
details were elucidated within the membrane using high resolution ssNMR spectroscopy [92]. The outer membrane protein AIL from Yersinia pestis, a key component in the infection process which interacts with human protein vitronectin, has
been shown to interact with LPS present in outer membrane [78, 93]. Similarly
the structure of a 32 kDa β-barrel integral membrane protein from human; voltage
dependent anion channel (VDAC, controlling the ion transport across the outer
mitochondrial membrane) and its interaction with lipid membranes Dipalmitoylphosphatidyl-choline (DMPC) has been studied in liposomes and lipid crystals
[94].
9.3.2 Membrane Protein Structure and Function by Solution NMR
Solution NMR membrane protein samples include micelles, isotropic bicelles, and
nanodiscs, some of them are shown in Fig. 27. The proteins inserted in these
membrane models reorient rapidly hence they are in solution NMR dynamics range.
Micelles are formed from detergents and normally the signal intensity is very good
and resolution is better, however detergents interact with proteins and in due course
of time nanodiscs started to become very popular as membrane model for solution
NMR of proteins [95–97]. In nanodiscs the sized of the lipid discs are controlled by
membrane scaffold proteins (MSPs). Different sizes of the discs can be prepared by
changing the size of MSPs [98, 99]. Nanodisc model were popularized in solution
NMR of membrane proteins by Wagner group [100]. The structure of AIL has been
solved in nanodiscs also [78].
It has been shown that LPS in outer membrane of Yersinia pestis interacts with
AIL and co-operates in infection process. This was proved recently by Singh et al.,
that nanodiscs can be prepared where LPS can be inserted inside nanodisc (Fig. 27e)
[101] and it can provide us the details of the interaction of AIL with LPS [77].
The residues of AIL near the membrane and the side chains from His side chain
interacts with LPS. This interaction effectively thickens the membrane and helps
the bacterium to evade the immune system [102]. Another progress was studying
Cytp450, a family of enzymes involved in the catalysis of wide range of substrates.
Cytp450 and its redox partner cytochrome b 5 (cytb 5 ) were reconstituted within a
single nanodisc to study the functional process using NMR spectroscopy [103]. A
recent progress in this area which is subject of active research these day is to replace
MSPs with polymers to prepare more stable and useful nanodisc [104].