Proteomic analysis methods for characterization of proteins from the salivary gland secretions of the medicinal leech during different seasons

Salivary gland secretion (SGS) of the medicinal leech Hirudo medicinalis in summer and winter was studied by proteomic analysis methods, and season-associated difference was found in the distribution of fractionated proteins with the same pattern of their positions. Differences were detected for proteins with molecular weights from 15 to 250 kD fractionated by two-dimensional SDS-PAGE and for 2-10- and 10-60-kD proteins analyzed by SELDI-MS. Thirty-two and 20 proteins were detected by MALDI-TOF-MS in the high-molecular-weight fraction of the summer and winter SGS, respectively, isolated from the corresponding two-dimensional electrophoregrams, and this was less than 20% of the total SGS protein. The N-terminal amino acid sequences were determined for 12 proteins. The peptide maps and N-terminal amino acid sequences of the proteins studied were identified, and no known proteins were revealed. These findings suggest a high content of newly revealed proteins in SGS of medicinal leech, and this correlates with multiple positive clinical effects of hirudotherapy realized through SGS, but the mechanisms of these effects remain unclear.