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Acetylation of lysine 92 improves the chaperone and anti-apoptotic activities of human ?B-crystallin.

ABSTRACT: ?B-Crystallin is a chaperone and an anti-apoptotic protein that is strongly expressed in many tissues, including the lens, retina, heart, and kidney. In the human lens, several lysine residues in ?B-crystallin are acetylated. We have previously shown that such acetylation is predominant at lysine 92 (K92) and lysine 166 (K166). We have investigated the effect of lysine acetylation on the structure and functions of ?B-crystallin by the specific introduction of an N(?)-acetyllysine (AcK) mimic at K92. The introduction of AcK slightly altered the secondary and tertiary structures of the protein. The introduction of AcK also resulted in an increase in the molar mass and hydrodynamic radius of the protein, and the protein became structurally more open and more stable than the native protein. The acetyl protein acquired higher surface hydrophobicity and exhibited 25-55% higher chaperone activity than the native protein. The acetyl protein had more client protein binding per subunit of the protein and higher binding affinity relative to that of the native protein. The acetyl protein was at least 20% more effective in inhibiting chemically induced apoptosis than the native protein. Molecular modeling suggests that acetylation of K92 makes the "?-crystallin domain" more hydrophobic. Together, our results reveal that the acetylation of a single lysine residue in ?B-crystallin makes the protein structurally more stable and improves its chaperone and anti-apoptotic activities. Our findings suggest that lysine acetylation of ?B-crystallin is an important chemical modification for enhancing ?B-crystallin's protective functions in the eye.

SUBMITTER: Nahomi RB

PROVIDER: S-EPMC3889837 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Acetylation of lysine 92 improves the chaperone and anti-apoptotic activities of human αB-crystallin.

Nahomi Rooban B RB Huang Rong R Nandi Sandip K SK Wang Benlian B Padmanabha Smitha S Santhoshkumar Puttur P Filipek Slawomir S Biswas Ashis A Nagaraj Ram H RH

Biochemistry 20131028 45

αB-Crystallin is a chaperone and an anti-apoptotic protein that is strongly expressed in many tissues, including the lens, retina, heart, and kidney. In the human lens, several lysine residues in αB-crystallin are acetylated. We have previously shown that such acetylation is predominant at lysine 92 (K92) and lysine 166 (K166). We have investigated the effect of lysine acetylation on the structure and functions of αB-crystallin by the specific introduction of an N(ε)-acetyllysine (AcK) mimic at ...[more]

PMID: 24128140

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Project description:Our previous work identified 23 low molecular weight (<3.5 kDa) crystallin peptides in the urea-soluble fractions of normal young, normal aged, and aged cataract human lenses. We found that one of these crystallin fragments, betaA3/A1(102-117) peptide (SDAYHIERLMSFRPIC), that are present in aged and cataract lens, increased the scattering of light by beta- and gamma-crystallins and alcohol dehydrogenase (ADH) and also reduced the chaperone-like activity of alphaB-crystallin. The present study was performed to identify the interacting sites of the betaA3/A1(102-117) peptide in alphaB-crystallin.betaA3/A1(102-117) peptide was first derivatized with sulfo-succinimidyl-2-[6-(biotinamido)-2-{p-azidobenzamido}-hexanoamido] ethyl-1-3 dithio propionate (sulfo-SBED), a photoactivable, heterotrifunctional biotin-containing cross-linker. The biotin-derivatized peptide was then incubated with alphaB-crystallin at 37 degrees C for 2 h to allow complex formation followed by photolysis to facilitate the transfer of the biotin label from the peptide to alphaB-crystallin. Label transfer was confirmed by western blot, and the labeled alphaB-crystallin was digested with trypsin. Tryptic peptides from alphaB-crystallin carrying the biotin label were purified by avidin affinity chromatography, and betaA3/A1(102-117) peptide interacting sites in alphaB-crystallin were identified by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and nanospray quadrupole time-of-flight mass spectrometry (QqTOF MS/MS).We found that the betaA3/A1(102-117) peptide interacted with alphaB-crystallin regions (70)LEKDR(74), (83)HFSPEELKVK(92), (91)VKVLGDVIEVHGK(103), (93)VLGDVIEVHGKHEER(107), and (121)KYR(123), which are part of the alpha-crystallin domain, and were previously shown to be part of the functional chaperone site in alphaB-crystallin. The betaA3/A1(102-117) peptide also interacted with regions at the COOH-terminal extension of alphaB-crystallin, (150)KQVSGPER(157), (164)EEKPAVTAAPK(174), and (164)EEKPAVTAAPKK(175). When two of the hydrophobic residues of betaA3/A1(102-117) peptide were replaced with hydrophilic residues, the resulting substituted peptide, SDADHGERLMSFRPIC, did not show the anti-chaperone property.This study confirmed the interactions between a low molecular weight peptide derived from betaA3/A1-crystallin found in aged and cataract lenses and alphaB-crystallin. The binding of betaA3/A1(102-117) peptide to the chaperone site and the COOH-terminal extension of alphaB-crystallin may explain its anti-chaperone property.

Dataset Information

Acetylation of lysine 92 improves the chaperone and anti-apoptotic activities of human ?B-crystallin.

Publications

Acetylation of lysine 92 improves the chaperone and anti-apoptotic activities of human αB-crystallin.

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