revision preference src: These four are highly interconnected in their functions in surfactant. Though the mechanism is not yet understood, SP-B functions in the post-translational modification of SP-C, and mature SP-C is not formed without SP-B. <SEP> tgt: These four are highly interconnected in their functions in surfactant. For example, though the mechanism is not yet understood, SP-B functions in the post-translational modification of SP-C, and mature SP-C is not formed without SP-B.