Studying noncovalent protein complexes by electrospray ionization mass spectrometry

Abstract

Electrospray ionization mass spectrometry has been used to baggage carriers, providing transport to important destinastudy protein interactions driven by noncovalent forces. The tions. In other cases, proteins require a partner to fulfill gentleness of the electrospray ionization process allows intact their crucial task in life. Generally, proteins as a class are protein complexes to be directly detected by mass spectrometry.nondiscriminating, interacting with a variety of species, Evidence from the growing body of literature suggests that the such as other proteins, peptides, oligonucleotides, metal ESI-MS observations for these weakly bound systems reflect, to ions, and other small molecules. Several protein systems some extent, the nature of the interaction found in the condensed are functionally active only when one or several copies of phase. Stoichiometry of the complex can be easily obtained from itself are in the vicinity (the quaternary structure of a the resulting mass spectrum because the molecular weight of protein). However, as with the macroscopic world, each the complex is directly measured. For the study of protein interindividual protein species may have preferences for a paractions, ESI-MS is complementary to other biophysical methods, such as NMR and analytical ultracentrifugation. However, mass ticular partner.

Native ESI Mass Spectrometry Can Help to Avoid Wrong Interpretations from Isothermal Titration Calorimetry in Difficult Situations

“…We note that the distribution of these probability values does not show any correlation with the affinity of the peptide ligand for its protein target but, instead, shows a clear correlation with the nature of the peptide (Supplementary Figure S7). This is in agreement with the conclusion from another study on protein–peptide interactions [23]. Gathering the results from [13] (which, apart one case among six, did not bear on protein–peptide interaction) also revealed a complete lack of correlation between and P (not shown).…”

Structure Relaxation Approximation (SRA) for Elucidation of Protein Structures from Ion Mobility Measurements (II). Protein Complexes

“…This observation supports the notion that the charge state of the detected protein ions does not profoundly influence the retention of native interactions (in the absence of overt changes to the detected cross sections), , which is expected until the point that the added protons are close enough to interact or disrupt salt bridges. Hence, overall, our observations support previous literature ,,,,− that proposes that significant structural reorganization of the native polypeptide chains of protein complexes is unlikely during native IM/MS measurements, except for flexible regions such as termini or loops.…”

“…Taken together, the fraction of native contacts calculated for the structures predicted by the SRA method highlights strong retention of the overall protein complexes and confirms notions made in prior literature in this regard. ,− Further, the SRA supports prior reports , that the charge states observed under native IM/MS measurements for the same protein complex exert only a negligible impact on the retention of native contacts. Finally, the dominant binding interfaces between polypeptide chains in the complexes studied here appear retained largely to the same extent as native contacts within the polypeptide chains.…”

Probing metal ion binding and conformational properties of the colicin E9 endonuclease by electrospray ionization time‐of‐flight mass spectrometry

“…Despite the very high affinity of the E9 DNase‐Im9 complex observed in solution, in the gas‐phase disruption of the protein–protein interaction occurs before dissociation of the protein–metal ion interaction. This is in accordance with the emerging view that electrostatic interactions are enhanced, whereas the hydrophobic effect becomes less significant in the gas phase (Loo 1997; Smith et al 1997a,b).…”