EXPRESSION, RECONSTITUTION AND CHARACTERIZATION OF PROLIXIN-S AS A VASODILATOR - A SALIVARY-GLAND NITRIC-OXIDE-BINDING HEMOPROTEIN OF RHODNIUS-PROLIXUS

Prolixin-S, an anticoagulant from the salivary gland of the blood-suck ing insect Rhodnius prolixus is also one of the members of salivary gl and hemoproteins. We produced recombinant protein using a baculovirus- insect cell expression system, reconstituted the hemoprotein and made some characterization of it as a nitric oxide carrier. The reconstitut ed protein exhibited the absorption spectrum of a high-spin ferric hem oprotein with a Soret absorption peak at 400 nm. By binding nitric oxi de (NO-prolixin-S), the Soret band shifted from 400 nm to 420 nm and t wo sharp bands (Q bands, at 535 nm and 565 nm) also appeared in the vi sible region. In a bioassay with aortic smooth muscle, NO-prolixin-S s howed strong relaxation activity in a dose-dependent manner, which dem onstrated that prolixin-S really acts as an NO carrier. A Soret absorp tion change also indicated that nitric oxide was gradually released un der these conditions (pH 7.4 and 37 degrees C). However, at low temper ature (20 degrees C) and/or low pH (pH 6), which mimic those in the in sect's salivary glands, the releasing became very slow. These differen t NO-binding properties would enable prolixin-S to reserve nitric oxid e in the salivary glands and release it in the host's blood vessels.