Low-Barrier Hydrogen Bonds and Enzymic Catalysis

Cleland, W. W.; Kreevoy, Maurice M.

doi:10.1126/science.8009219

Cited by 1,144 publications

(946 citation statements)

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“…(4) The hydrogen bond between an Asp carboxylate oxygen and a phosphate oxygen, which is extremely short (2.432 A distance) as established in the ultra-high resolution structures, confers the exquisite specificity of the PBP and the phosphate transport system. Although the distance is within the proposed range of low barrier hydrogen bonds with estimated energies of 12-24 kcal/mol (Hibbert & Emsley, 1990;Cleland & Kreevoy, 1994). the contribution of the short hydrogen bond to the phosphate binding affinity is no better than that of a normal hydrogen bond.…”

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confidence: 63%

Dominant role of local dipolar interactions in phosphate binding to a receptor cleft with an electronegative charge surface: Equilibrium, kinetic, and crystallographic studies

et al. 1998

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Stringent specificity and complementarity between the receptor, a periplasmic phosphate-binding protein (PBP) with a two-domain structure, and the completely buried and dehydrated phosphate are achieved by hydrogen bonding or dipolar interactions. We recently found that the surface charge potential of the cleft between the two domains that contains the anion binding site is intensely electronegative. This novel finding prompted the study reported here of the effect of ionic strength on the equilibrium and rapid kinetics of phosphate binding.

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confidence: 63%

Dominant role of local dipolar interactions in phosphate binding to a receptor cleft with an electronegative charge surface: Equilibrium, kinetic, and crystallographic studies

et al. 1998

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“…In contrast, the estimated AG here is lower than the free energy values derived by Fersht and coworkers (1,4) from site-directed mutagenesis studies. The lower value is attributed to the relatively exposed aqueous environment in which the present (19,20). In the case at hand, the alternating hydrogen bond donor-acceptor arrangement of the two new hydrogen bonds formed results in some unfavorable secondary interactions (21).…”

Section: Resultsmentioning

confidence: 98%

Hydrogen bonding in water using synthetic receptors.

Kato

Conn

Rebek

1995

Proc. Natl. Acad. Sci. U.S.A.

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Four water-soluble adenine receptors were synthesized to study the influence of hydrophobic interactions and hydrogen bonding on molecular recognition in aqueous solution. Association constants were measured in aqueous solution at five temperatures from 3-27°C (pH 6, 51 mM ionic strength). For the mono(imide) receptors, AH was -5.8 kcal/mol (carbazole) and -9.2 kcal/mol (naphthalene). The entropy of association for these was -13 cal mol-l K-1 (carbazole) and -26 cal mol-l K-1 (naphthalene). The carbazole bis(imide) receptor showed a binding enthalpy of -7.4 kcal/mol and entropy of -18 cal mol-l K-1. From this the free energy at 298 K of a single hydrogen bond is estimated to be only 0.2 kcal/mol. The enthalpy of a single hydrogen bond in this solvent-exposed system is estimated to be, at most, 0.8 kcal/mol, indicating that enthalpy just compensates for the unfavorable entropy in this system. These values reflect stronger hydrophobic interactions with the more polarizable naphthalene, as well as enthalpy-entropy compensation effects.

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“…A serine residue (pK about 13 in water) donates its hydroxyl proton to a histidine residue. Histidine is "activated" as a proton acceptor by a further, strong hydrogen bond with an aspartic acid (104,105).…”

Section: Discussionmentioning

confidence: 99%

Tyrosine-Z in Oxygen-Evolving Photosystem II: A Hydrogen-Bonded Tyrosinate

1998

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In oxygen-evolving photosystem II (PSII), a tyrosine residue, D1Tyr161 (Y Z ), serves as the intermediate electron carrier between the catalytic Mn cluster and the photochemically active chlorophyll moiety P 680 . A more direct catalytic role of Y Z , as a hydrogen abstractor from bound water, has been postulated. That Y Z ox appears as a neutral (i.e. deprotonated) radical, Y Z • , in EPR studies is compatible with this notion. Data based on electrochromic absorption transients, however, are conflicting because they indicate that the phenolic proton remains on or near to Y Z ox . In Mn-depleted PSII the electron transfer between Y Z and P 680 + can be almost as fast as in oxygen-evolving material, however, only at alkaline pH. With an apparent pK of about 7 the fast reaction is suppressed and converted into an about 100-fold slower one which dominates at acid pH. In the present work we investigated the optical difference spectra attributable to the transition Y Z f Y Z ox as function of the pH. We scanned the UV and VIS range and used Mn-depleted PSII core particles and also oxygen-evolving ones. Comparing these spectra with published in vitro and in vivo spectra of phenolic compounds, we arrived at the following conclusions: In oxygen-evolving PSII Y Z resembles a hydrogen-bonded tyrosinate, Y Z (-) ‚‚‚H (+) ‚B. The phenolic proton is shifted toward a base B already in the reduced state and even more so in the oxidized state. The retention of the phenolic proton in a hydrogen-bonded network gives rise to a positive net charge in the immediate vicinity of the neutral radical Y Z • . It may be favorable both for the very rapid reduction by Y Z of P 680 + and for electron (not hydrogen) abstraction by Y Z • from the Mn-water cluster.Photosystem II (PSII) 1 produces molecular oxygen from water. It is located in photosynthetic membranes of plants and cyanobacteria. The inner core of PSII is a heterodimer of the D1D2 subunits which show homology with the L and M subunits of the purple bacterial RC (1). The primary electron donor of PSII, P 680 , is located close to the lumenal side of the membrane. The absorption of a quantum of light drives the charge separation between P 680 and the quinone acceptor at the stromal side (2). The very high redox potential of P 680 + drives water oxidation. It is a four-stepped process with at least four increasingly oxidized, metastable states S 0 to S 3 , plus a transient state S 4 that decays in milliseconds into S 0 under release of O 2 . P 680 + is reduced (in nanoseconds) by a redox-active tyrosine residue, Y Z (D1Tyr161 (3, 4)). Y Z ox is, in turn, reduced in microseconds by the oxygenevolving complex (OEC). The structure and exact location of the OEC is still ill-defined. It is formed by four manganese atoms (5, 6), possibly another redox cofactor, X (7-9), plus at least one Cl -ion (10) and one Ca 2+ (11, 12) ion. These cofactors serve various functions during water oxidation: The Mn cluster stores at least two of the oxidizing equivalents (namely on transitions S ...

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Low-Barrier Hydrogen Bonds and Enzymic Catalysis

Cited by 1,144 publications

References 34 publications

Dominant role of local dipolar interactions in phosphate binding to a receptor cleft with an electronegative charge surface: Equilibrium, kinetic, and crystallographic studies

Dominant role of local dipolar interactions in phosphate binding to a receptor cleft with an electronegative charge surface: Equilibrium, kinetic, and crystallographic studies

Hydrogen bonding in water using synthetic receptors.

Tyrosine-Z in Oxygen-Evolving Photosystem II: A Hydrogen-Bonded Tyrosinate

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