Figure 3.

MR binding to collagen depends on the FNII domain protruding loop. A, alignment of FNII domain sequences from MR, PLA₂R1, and MR-loop-P (MR-loop-P, MR mutant receptor with residues Thr-183–Leu-192 replaced by the corresponding residues from PLA₂R1). The amino acid numbering here follows the MR sequence (accession no. NP_032651). B, western blotting analysis for the detection of MR in CHO-K1 cells transfected with the indicated constructs (top panel). Loading controls were included as described in the legend to Fig. 1 (bottom panel). C and D, assay for uptake of radiolabeled mannose-BSA (C) and collagen type I (D) by mock CHO-K1 cells and cells expressing MR or MR-loop-P. The uptake of collagen type I was normalized to the uptake of mannose-BSA to adjust for differences in the receptors' expression levels (see “Experimental procedures”). Data are presented as mean ± S.D. with individual data points also shown. Analysis was performed in triplicate.