4 research outputs found
Similar Albeit Not the Same: In-Depth Analysis of Proteoforms of Human Serum, Bovine Serum, and Recombinant Human Fetuin
Fetuin,
also known as alpha-2-Heremans Schmid glycoprotein (AHSG),
belongs to some of the most abundant glycoproteins secreted into the
bloodstream. In blood, fetuins exhibit functions as carriers of metals
and small molecules. Bovine fetuin, which harbors 3 N-glycosylation
sites and a suggested half dozen O-glycosylation sites, has been used
often as a model glycoprotein to test novel analytical workflows in
glycoproteomics. Here we characterize and compare fetuin in depth,
using protein from three different biological sources: human serum,
bovine serum, and recombinant human fetuin expressed in HEK-293 cells,
with the aim to elucidate similarities and differences between these
proteins and the post-translational modifications they harbor. Combining
data from high-resolution native mass spectrometry and glycopeptide
centric LC-MS analysis, we qualitatively and quantitatively gather
information on fetuin protein maturation, N-glycosylation, O-glycosylation,
and phosphorylation. We provide direct experimental evidence that
both the human serum and part of the recombinant proteins are processed
into two chains (A and B) connected by a single interchain disulfide
bridge, whereas bovine fetuin remains a single-chain protein. Although
two N-glycosylation sites, one O-glycosylation site, and a phosphorylation
site are conserved from bovine to human, the stoichiometry of the
modifications and the specific glycoforms they harbor are quite distinct.
Comparing serum and recombinant human fetuin, we observe that the
serum protein harbors a much simpler proteoform profile, indicating
that the recombinant protein is not ideally engineered to mimic human
serum fetuin. Comparing the proteoform profile and post-translational
modifications of human and bovine serum fetuin, we observe that, although
the gene structures of these two proteins are alike, they represent
quite distinct proteins when their glycoproteoform profile is also
taken into consideration
Similar Albeit Not the Same: In-Depth Analysis of Proteoforms of Human Serum, Bovine Serum, and Recombinant Human Fetuin
Fetuin,
also known as alpha-2-Heremans Schmid glycoprotein (AHSG),
belongs to some of the most abundant glycoproteins secreted into the
bloodstream. In blood, fetuins exhibit functions as carriers of metals
and small molecules. Bovine fetuin, which harbors 3 N-glycosylation
sites and a suggested half dozen O-glycosylation sites, has been used
often as a model glycoprotein to test novel analytical workflows in
glycoproteomics. Here we characterize and compare fetuin in depth,
using protein from three different biological sources: human serum,
bovine serum, and recombinant human fetuin expressed in HEK-293 cells,
with the aim to elucidate similarities and differences between these
proteins and the post-translational modifications they harbor. Combining
data from high-resolution native mass spectrometry and glycopeptide
centric LC-MS analysis, we qualitatively and quantitatively gather
information on fetuin protein maturation, N-glycosylation, O-glycosylation,
and phosphorylation. We provide direct experimental evidence that
both the human serum and part of the recombinant proteins are processed
into two chains (A and B) connected by a single interchain disulfide
bridge, whereas bovine fetuin remains a single-chain protein. Although
two N-glycosylation sites, one O-glycosylation site, and a phosphorylation
site are conserved from bovine to human, the stoichiometry of the
modifications and the specific glycoforms they harbor are quite distinct.
Comparing serum and recombinant human fetuin, we observe that the
serum protein harbors a much simpler proteoform profile, indicating
that the recombinant protein is not ideally engineered to mimic human
serum fetuin. Comparing the proteoform profile and post-translational
modifications of human and bovine serum fetuin, we observe that, although
the gene structures of these two proteins are alike, they represent
quite distinct proteins when their glycoproteoform profile is also
taken into consideration
Similar Albeit Not the Same: In-Depth Analysis of Proteoforms of Human Serum, Bovine Serum, and Recombinant Human Fetuin
Fetuin,
also known as alpha-2-Heremans Schmid glycoprotein (AHSG),
belongs to some of the most abundant glycoproteins secreted into the
bloodstream. In blood, fetuins exhibit functions as carriers of metals
and small molecules. Bovine fetuin, which harbors 3 N-glycosylation
sites and a suggested half dozen O-glycosylation sites, has been used
often as a model glycoprotein to test novel analytical workflows in
glycoproteomics. Here we characterize and compare fetuin in depth,
using protein from three different biological sources: human serum,
bovine serum, and recombinant human fetuin expressed in HEK-293 cells,
with the aim to elucidate similarities and differences between these
proteins and the post-translational modifications they harbor. Combining
data from high-resolution native mass spectrometry and glycopeptide
centric LC-MS analysis, we qualitatively and quantitatively gather
information on fetuin protein maturation, N-glycosylation, O-glycosylation,
and phosphorylation. We provide direct experimental evidence that
both the human serum and part of the recombinant proteins are processed
into two chains (A and B) connected by a single interchain disulfide
bridge, whereas bovine fetuin remains a single-chain protein. Although
two N-glycosylation sites, one O-glycosylation site, and a phosphorylation
site are conserved from bovine to human, the stoichiometry of the
modifications and the specific glycoforms they harbor are quite distinct.
Comparing serum and recombinant human fetuin, we observe that the
serum protein harbors a much simpler proteoform profile, indicating
that the recombinant protein is not ideally engineered to mimic human
serum fetuin. Comparing the proteoform profile and post-translational
modifications of human and bovine serum fetuin, we observe that, although
the gene structures of these two proteins are alike, they represent
quite distinct proteins when their glycoproteoform profile is also
taken into consideration
Parsimonious Charge Deconvolution for Native Mass Spectrometry
Charge
deconvolution infers the mass from mass over charge (<i>m</i>/<i>z</i>) measurements in electrospray ionization
mass spectra. When applied over a wide input <i>m</i>/<i>z</i> or broad target mass range, charge-deconvolution algorithms
can produce artifacts, such as false masses at one-half or one-third
of the correct mass. Indeed, a maximum entropy term in the objective
function of MaxEnt, the most commonly used charge deconvolution algorithm,
favors a deconvolved spectrum with many peaks over one with fewer
peaks. Here we describe a new “parsimonious” charge
deconvolution algorithm that produces fewer artifacts. The algorithm
is especially well-suited to high-resolution native mass spectrometry
of intact glycoproteins and protein complexes. Deconvolution of native
mass spectra poses special challenges due to salt and small molecule
adducts, multimers, wide mass ranges, and fewer and lower charge states.
We demonstrate the performance of the new deconvolution algorithm
on a range of samples. On the heavily glycosylated plasma properdin
glycoprotein, the new algorithm could deconvolve monomer and dimer
simultaneously and, when focused on the <i>m</i>/<i>z</i> range of the monomer, gave accurate and interpretable
masses for glycoforms that had previously been analyzed manually using <i>m</i>/<i>z</i> peaks rather than deconvolved masses.
On therapeutic antibodies, the new algorithm facilitated the analysis
of extensions, truncations, and Fab glycosylation. The algorithm facilitates
the use of native mass spectrometry for the qualitative and quantitative
analysis of protein and protein assemblies