The largest arthropod cuticular protein family， CPR， has the Rebers and Riddiford (R&R) Consensus that in an extended form confers chitin-binding properties. Two forms of the Consensus， RR-1 and RR-2， have been recognized and initial data suggested that the RR-1 and RR-2 proteins were present in different regions within the cuticle itself. Thus， RR-2 proteins would contribute to exocuticle that becomes sclerotized， while RR-1s would be found in endocuticle that remains soft. An alternative， and more common， suggestion is that RR-1 proteins are used for soft， flexible cuticles such as intersegmental membranes， while RR-2s are associated with hard cuticle such as sclerites and head capsules. W... More
The largest arthropod cuticular protein family， CPR， has the Rebers and Riddiford (R&R) Consensus that in an extended form confers chitin-binding properties. Two forms of the Consensus， RR-1 and RR-2， have been recognized and initial data suggested that the RR-1 and RR-2 proteins were present in different regions within the cuticle itself. Thus， RR-2 proteins would contribute to exocuticle that becomes sclerotized， while RR-1s would be found in endocuticle that remains soft. An alternative， and more common， suggestion is that RR-1 proteins are used for soft， flexible cuticles such as intersegmental membranes， while RR-2s are associated with hard cuticle such as sclerites and head capsules. We used TEM immunogold detection to localize the position of several RR-1 and RR-2 proteins in the cuticle of Anopheles gambiae. RR-1s were localized in the procuticle of the soft intersegmental membrane except for one protein found in the endocuticle of hard cuticle. RR-2s were consistently found in hard cuticle and not in flexible cuticle. All RR-2 antibodies localized to the exocuticle and four out of six were also found in the endocuticle. Hence the location of RR-1s and RR-2s depends more on properties of individual proteins than on either hypothesis.
