AESTIVATION INDUCTION AND EVIDENCE OF CONFORMATIONAL DIFFERENCES BETWEEN OXY-HAEMOCYANIN AND DEOXY-HAEMOCYANININ AESTIVATING AND NON-AESTIVATING SNAILS

ABSTRACT

Haemocyanin is a high molecular weight, dioxygen, transport, copper-glycoprotein with a di-copper active site found in the haemolymph of several marine and terrestrial invertebrates belonging to the phyla Mollusca and Arthropoda. Haemocyanin exists in two distinct conformers: the T-conformer (Tense) and the R-conformer (Relaxed).Knowledge of the molecular architecture around the copper atoms in the active site of haemocyanin is important in understanding how these proteins reversibly bind oxygen. Induction of aestivation and the evidence of conformational differences between oxy-haemocyanin and deoxy-haemocyanin in aestivating and non-aestivating snails was studied.Aestivation induction was studied by treating five groups of snails (groups A, B, C, D and E) with respective volumes of oxy-haemocyanin from aestivating snails, respective volumes of oxy-haemocyanin from non-aestivating snails and respective volumes of distilled water. Evidence of conformational differences between oxy-haemocyanin and deoxy-haemocyanin was also studied by treating the haemolymph of two snail samples (Snail 1 and Snail 2) with nitrogen gas.After the induction of aestivation, it was observed that the snails in groups A, B and C administered with the respective volumes of haemolymph extracted from aestivating rsnails began to synthesize epiphragm layer on the 4th day after injection, on the 5th day after injection, the epiphragm layer was completely formed. Whereas the snails in groups D and E began to synthesize epiphragm layer on the 5th day, on the 6th day, the epiphragm layer was completely formed. It was also observed that the snails in groups A, B and C that were injected with haemolymph extracted from non-aestivating snails beganto synthesize epiphragm layer on the 4th day, on the 5th day, the epiphragm layer was completely formed. It was also observed that the snails in groups D and E that were injected with different volumes of water, began to synthesize epiphragm layer on the 3rd day, at about 4 days and 8hours after injection, the epiphragm layer was completely formed. Whereas the snails in groups A, B and C began to synthesize epiphragm layer on the 4th day, at about 5 days after injection, the epiphragm layer was completely formed. Results from the UV-Visible scanning showed that oxyhaemocyanin exhibited spectral activity both in the near-UV region and in the mid-UV region, whereas deoxyhaemocyanin only showed spectral activity in the near-UV region.