NOS1 and Stroke: Nitric Oxide Synthase 1. The protein encoded by this gene belongs to the family of nitric oxide synthases, which synthesize nitric. Nitric oxide is a reactive free radical, which acts as a biologic mediator in several processes, including neurotransmission, and antimicrobial and antitumoral activities. In the brain and peripheral nervous system, nitric oxide has been implicated in neurotoxicity associated with stroke and neurodegenerative diseases, neural regulation of smooth muscle, including peristalsis, and penile erection.