pK change of imidazole groups in bovine serum albumin due to the conformational change at neutral pH

Bruin, Simon H. de; Harmsen, B.J.M.; Janssen, Lambert H.M.; Miranda, J. F. Rodrigues de; Os, G.A.J. Van

doi:10.1021/bi00793a009

Cited by 129 publications

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References 21 publications

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“…This apparent increase may not reside in InpA activity per se , but may result from structural changes in the albumin molecule occurring in solution at high pH [ 23 , 24 ]. Albumin displays a greater thermal stability at pH 6.4 than at pH 7.4 [ 25 ], undergoing a conformational change around pH 7.5 referred to as the N → B transition [ 26 ], pointing to the B form being more susceptible to InpA, as has been demonstrated for trypsin [ 27 ]. This may be physiologically relevant as diseased periodontal pockets and the inflamed gingival sulcus are slightly alkaline [ 28 , 29 , 30 ].…”

Section: Resultsmentioning

confidence: 99%

Breakdown of albumin and haemalbumin by the cysteine protease interpain A, an albuminase of Prevotella intermedia

et al. 2015

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BackgroundPrevotella intermedia is a Gram-negative black-pigmenting oral anaerobe associated with periodontitis in humans, and has a haem requirement for growth, survival and virulence. It produces an iron porphyrin-containing pigment comprising monomeric iron (III) protoporphyrin IX (Fe(III)PPIX.OH; haematin). The bacterium expresses a 90-kDa cysteine protease termed interpain A (InpA) which both oxidizes and subsequently degrades haemoglobin, releasing haem. However, it is not known whether the enzyme may play a role in degrading other haem-carrying plasma proteins present in the gingival sulcus or periodontal pocket from which to derive haem. This study evaluated the ability of InpA to degrade apo- and haem-complexed albumin.ResultsAlbumin breakdown was examined over a range of pH and in the presence of reducing agent; conditions which prevail in sub- and supra-gingival plaque. InpA digested haemalbumin more efficiently than apoalbumin, especially under reducing conditions at pH 7.5. Under these conditions InpA was able to substantially degrade the albumin component of whole human plasma.ConclusionsThe data point to InpA as an efficient “albuminase” with the ability to degrade the minor fraction of haem-bound albumin in plasma. InpA may thus contribute significantly to haem acquisition by P. intermedia under conditions of low redox potential and higher pH in the inflamed gingival crevice and diseased periodontal pocket where haem availability is tightly controlled by the host.

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Section: Resultsmentioning

confidence: 99%

Breakdown of albumin and haemalbumin by the cysteine protease interpain A, an albuminase of Prevotella intermedia

et al. 2015

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Salt bonding in proteins. A model for the abnormal hydrogen ion titration and the strong anion binding of serum albumin

Arvidsson

1972

Biopolymers

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SynopsisSerum albumin undergoes a conformational change a t pH 4, known as the N-F transition. In the customary LinderstrZm-Lang treatment of hydrogen ion titration, the carboxyl groups in serum albumin either have an abnormally low pK, or are buried in charged form, and the LinderstrZm-Lang charging parameter w decreases dramatically at the N-F isomerization. In the present paper partition functions are derived and distribution functions are calculated for a model permitting salt bonding between the positively and negatively charged sites on a macromolecule. The N-form has an abnormally high salt bonding constant whereas that of the F-form corresponds to that of small ions. The result obtained is consistent with a "normal" intrinsic pK of the carboxyl groups of serum albumin without burying of any charges and with an unchanged W.Further, it is shown that the "abnormal salt bonding" of serum album'n can explain its unusual ability to bind anions. Theoretical binding curves are calculated and compared with literature data of the C1-binding of serum albumin. The relation of the present model to other models of hydrogen ion and anion binding to proteins is discussed. Some additional consequences of the present model are pointed out; a transition in the alkaline range, analogous to the acid transition, seems probable. Literature data support the existence of such a transition but do not allow detailed calculations a t present.A general, thermodynamic treatment of the interactions between small ligands and macromolecules is outlined. Important points are the choice of the statistical-mechanical ensemble and considerations of the fluctuations about the mean binding, if (i)there are not only a ligand-locus interaction but also interligand interactions (in particular intdigand attraction), or (ii) there is a conformational change in themacromolecule depending on the ligand binding. In these cases, the binding isotherms obtained from thermodynamically closed systems (canonical ensemble)) may erroneously indicate a distribution about a single probability maximum, i.e., the statistical mean binding N, and fluctuations about this value. The description of a phase change in a bound phase or a change in the "internal" self-interactions of a macromolecule requires a binding equation permitting distributions about two maxima, i.e., (i) N1* < iV ("thin" phase) and Nz* > iV (L'condensed" phase) or (ii) two macromolecular conformations P', and P", having occupancy numbers iV, and ITz, respectively. The N-F transition is an example illustrating the relation between the complete distribution functions and the two-state approximation. 2197

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pH‐jump titration of the tyrosyl groups of bovine plasma albumin

et al. 1984

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SynopsisIonization properties of the tyrosyl groups of bovine plasma albumin in various conformational states-the native state (N), the two acid states (F and E), and the state (B) stable at slightly alkaline pH-were studied by means of a stopped-flow pH-jump technique. The technique allows us to obtain the tyrosyl titration curve in a conformational state that is unstable in the pH region of the titration. The pH jumps from the N and B states to various alkaline pH's, where the tyrosines ionize to bring about a timedependent increase in absorption at 296 nm, indicating that a number of the tyrosines buried initially become susceptible to ionization as a result of the alkaline transition occurring above pH 10.8. Extrapolation of the observed absorption change to zero time gives a spectrophotometric titration curve in the initial conformational state. Only 3040% of the 19 tyrosines of the protein can ionize both in the N and the B state a t pH 12. The pH jumps from the F and E states, on the other hand, give a decrease in absorption between pH 9 and 11.7, indicating that the tyrosyl groups initially exposed are remasked by refolding after the pH jumps, and the zero-time titration curves show that essentially all the tyrosyl groups ionize normally in these acid states. The results are discussed in relation to the known results of the tyrosyl exposure of the protein measured by other techniques, and the consistency among them demonstrates the effectiveness of the pH-jump titration method. Hydrogen bonding between the abnormal tyrosyl and carboxylate groups as'a mechanism to stabilize native albumin is suggested from characteristics of the alkaline transition, which also involves the exposure of the tyrosyl groups, and from the tyrosyl titration curves in the native and acid states.

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pK change of imidazole groups in bovine serum albumin due to the conformational change at neutral pH

Cited by 129 publications

References 21 publications

Breakdown of albumin and haemalbumin by the cysteine protease interpain A, an albuminase of Prevotella intermedia

Breakdown of albumin and haemalbumin by the cysteine protease interpain A, an albuminase of Prevotella intermedia

Salt bonding in proteins. A model for the abnormal hydrogen ion titration and the strong anion binding of serum albumin

pH‐jump titration of the tyrosyl groups of bovine plasma albumin

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