The plant growth regulator ethylene is a crucial hormone in fruit ripening, flower senescence, seedling growth, and seed germination. Ethylene is produced naturally by many plant tissues, is often regulated by internal signals within the plant and acts in response to environmental stress. It is believed that there is a Cu(I) cofactor responsible for the binding of ethylene in the ethylene receptors known as ETR1. In the ETR1 receptor, there is an identified binding location in a 128 amino acid sequence that contains three alpha helices. There are four identified amino acids in the sequence that may ligate the Cu(I) cofactor: histidine, aspartic acid, cysteine, and tyrosine. Very little is understood about how the ethylene binds to the Cu(I) in ETR1. Likewise, very little is known about how 1-MCP inhibits ethylene in the binding site. In this work, the bonding interactions between Cu(I) coordination complexes with ethylene and 1-MCP are investigated. Density functional calculations (B3LYP/6-32G*) were performed utilizing Spartan ’14 software (Wavefunction Inc.). Cu (I) complexes were modeled with varying ligands focusing on their interactions with 1-MCP and ethylene. The complexes studied involved coordination of 2, 3 and 4 ligands. These ligands included CN, CO, H2O, NH3, and benzene. The amino acids included in this study were histidine, cysteine, aspartic acid, and tyrosine. The carbon-carbon π-bond lengths, bond-angle of directly bonded hydrogen atoms, HOMO-LUMO energy gaps, and predicted IR spectra were modeled in order to determine likely moieties involved in the binding at the active site.

Molecular modeling of plant ripening receptors and their interactions with ethylene and ripening inhibitors

252nd National Meeting (2016)

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