Haemocyanin of some Oniscidea

Area of Science:

• Biochemistry
• Marine Biology
• Crustacean Physiology

Background:

• Haemocyanins are copper-containing respiratory proteins found in many arthropods and mollusks.
• Oniscidea (woodlice) possess haemocyanin in their hemolymph for oxygen transport.
• Understanding haemocyanin structure and function is crucial for invertebrate physiology.

Purpose of the Study:

• To characterize the quaternary structure of Oniscidea haemocyanin.
• To investigate the factors affecting the alkaline dissociation of the 16S haemocyanin component.
• To determine the amino acid composition of the 16S haemocyanin.

Main Methods:

• Ultracentrifugation to determine haemocyanin component sizes (16S, 5S, 24S).
• pH-dependent and cation-dependent dissociation studies.
• Amino acid analysis of the 16S haemocyanin component.

Main Results:

• Oniscidea haemocyanin is predominantly a 16S hexamer (90%), with minor 5S and 24S components.
• Alkaline dissociation of 16S haemocyanin is sensitive to pH and the presence of Ca2+ and Mg2+.
• The 16S component contains 23-24.5% acidic amino acids, 15-18% basic amino acids, and low levels of tryptophan and cysteine.

Conclusions:

• The 16S hexamer is the primary functional form of haemocyanin in Oniscidea.
• Environmental factors like pH and divalent cations play a role in regulating haemocyanin dissociation and potentially oxygen-binding.
• The amino acid profile of the 16S component provides insights into its structural stability and functional properties.