Properties of MMR-B3. The gene transcript (bottom) is composed of an 11 base 5'-end untranslated region (UTR), an 849 base coding region (rectangle), and a 34 base 3'-end UTR. The coding region begins with a 16 codon region encoding a signal peptide (light gray box) followed by 10 additional codons (hashed box) before the first of three repeats of a conserved motif (dark gray boxes). Arginines within each repeat are indicated with diamonds. The first two motifs are 87 codons each and differ at a single synonymous position; the third motif is truncated after codon 83 by a stop codon (TAA) and differs from the second by a single synonymous position. The 3'-end UTR bears no resemblance to the remainder of the motif. The first 41 amino acids of the predicted peptide (top) show the probability of each residue being part of a signal sequence (line) and the probability of each residue being on the carboxy side of the signal peptide cleavage site (histogram). The sequence logo to the right shows the N-terminal sequence of the 29 kD band, scaled to the frequency of each residue. The left arrow (below) shows the PCR primer matching the beginning of the first repeat, which also matches the N-terminal sequence of the 29 kD band. The right arrow represents the reverse primer. The predicted masses of the full-length peptide, the peptide without the signal region, and the peptide beginning with the first base of the first repeat (dark boxes only) are 30.9 kD, 29.2 kD, and 28.1 kD, respectively; the isoelectric points are 4.26, 4.16, and 4.02; and the charges at pH 8.0 are -9.4, -10.1, and -11.1.