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  1. Quantum mechanical tunnelling through the catalytic effects of A2451 ribosomal residue during a stepwise peptide bond formation
    Monajemi H, Md Zain S, Ishida T, Wan Abdullah WAT
    Biochem. Cell Biol., 2019 08;97(4):497-503.
    PMID: 30444637 DOI: 10.1139/bcb-2018-0220
    The search for the mechanism of ribosomal peptide bond formation is still ongoing. Even though the actual mechanism of peptide bod formation is still unknown, the dominance of proton transfer in this reaction is known for certain. Therefore, it is vital to take the quantum mechanical effects on proton transfer reaction into consideration; the effects of which were neglected in all previous studies. In this study, we have taken such effects into consideration using a semi-classical approach to the overall reaction mechanism. The M06-2X density functional with the 6-31++G(d,p) basis set was used to calculate the energies of the critical points on the potential energy surface of the reaction mechanism, which are then used in transition state theory to calculate the classical reaction rate. The tunnelling contribution is then added to the classical part by calculating the transmission permeability and tunnelling constant of the reaction barrier, using the numerical integration over the Boltzmann distribution for the symmetrical Eckart potential. The results of this study, which accounts for quantum effects, indicates that the A2451 ribosomal residue induces proton tunnelling in a stepwise peptide bond formation.
    Matched MeSH terms: Peptide Biosynthesis*
  2. Fulltext Sex-steroid regulation of relaxin receptor isoforms (RXFP1 & RXFP2) expression in the patellar tendon and lateral collateral ligament of female WKY rats
    Dehghan F, Muniandy S, Yusof A, Salleh N
    Int J Med Sci, 2014;11(2):180-91.
    PMID: 24465164 DOI: 10.7150/ijms.6283
    The incidence of non-contact knee injury was found higher in female than in male and is related to the phases of the menstrual cycle. This raised the possibility that female sex-steroids are involved in the mechanism underlying this injury via affecting the expression of the receptors for relaxin, a peptide hormone known to modulate ligament laxity. Therefore, this study aims to investigate the effect of sex-steroids on relaxin receptor isoforms (RXFP1 & RXFP2) expression in the ligaments and tendons of the knee.

    METHODS: Ovariectomized adult female WKY rats were treated with different doses of estrogen (0.2, 2, 20 μg/kg), progesterone (4mg) and testosterone (125 & 250μg/kg) for three consecutive days. At the end of the treatment, the animals were sacrificed and the patellar tendon and lateral collateral ligament were harvested for mRNA and protein expression analyses by Real Time PCR and Western blotting respectively.

    RESULTS: RXFP1, the main isoform expressed in these knee structures and RXFP2 showed a dose-dependent increase in expression with estrogen. Progesterone treatment resulted in an increase while testosterone caused a dose-dependent decrease in the mRNA and protein expression of both relaxin receptor isoforms.

    DISCUSSION: Progesterone and high dose estrogen up-regulate while testosterone down-regulates RXFP1 and RXFP2 expression in the patellar tendon and lateral collateral ligament of rat's knee.

    CONCLUSION: Relaxin receptor isoforms up-regulation by progesterone and high dose estrogen could provide the basis for the reported increase in knee laxity while down-regulation of these receptor isoforms by testosterone could explain low incidence of non-contact knee injury in male.

    Matched MeSH terms: Receptors, Peptide/biosynthesis*
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