. . .Their potent venom is the result of a presynaptic neurotoxin composed of two distinct peptide subunits.[13] The basic subunit (a phospholipase A2) is mildly toxic and apparently rather common in North American rattlesnake venoms.[14] The less common acidic subunit is not toxic by itself but, in combination with the basic subunit, produces the potent neurotoxin called “Mojave toxin.” Nearly identical neurotoxins have been discovered in five North American rattlesnake species besides C. scutulatus.[14] However, not all populations express both subunits. . . In people bitten by Venom A Mohave rattlesnakes (those outside the relatively small Venom B area in south-central Arizona), the onset of serious signs and symptoms can be delayed, sometimes leading to an initial underestimation of the severity of the bite.. . .