Figure 2.

Sucrose gradient interaction assay of recombinant Alb3 and Alb4 C-terminus variants with chloroplast ribosomes. The recombinant His-tagged C-terminal regions of Alb3 and Alb4 and the indicated deletion constructs were incubated with chloroplast ribosomes and loaded onto a sucrose density gradient. After ultracentrifugation, the gradient fractions were analyzed immunologically using antibodies against the His-tag (α-His) and the chloroplast ribosomal protein uL4c (α-uL4c). Sucrose density gradient centrifugation of the recombinant proteins in the absence of ribosomes was used as negative control. Alb3-C, C-terminal region of Alb3 (amino acids 350–462); Alb4-C, C-terminal region of Alb4 (amino acids 334–499). (A) Comparison of Alb3-C and Alb4-C. (B) A successive experimental series of 20 amino acid deletions introduced into the Alb3-C construct. (C) Targeted deletions of highly conserved arginine- and lysine-rich sequences within motif III and motif IV.