Protein synthesis by intracellular symbionts in two closely interrelated aphid species

An aphid endosymbiont in vivo synthesizes symbionin almost exclusively which is not produced in vitro by the same symbiont. While symbionin produced by the endosymbiont of the pea aphid is an acidic protein with a molecular weight of 63,000, that by the symbiont of the kondo aphid, the closest relative to the former, is a distinct, less acidic, molecule. While the two endosymbionts in vivo in old insects synthesize about 11 protein species in common, they produce many different proteins when incubated extracellularly.