Table 5.

Non-canonical cysteine content is low in SynVH-C and SynVH-SD birds.

		FR1	CDR1	FR2	CDR2	FR3	CDR3	FR4
SynVH-C	Single Cys	0	2	8	13	5	43	9
	Paired Cys	0	0	0	4 (CDSC)	0	3 (CWNFLC)	0
					2 (CC)
SynVH-SD	Single Cys	3	5	3	2	2	22	6
	Paired Cys	0	0	0	0	0	34 (CNDYYC)	0
							76 (CYYC)

Numbers refer to the number of unique sequences containing a single, unpaired Cys residue or two potentially paired Cys residues in the top 1,000 unique sequences from each bird (only human V regions were analyzed; total, n = 5,652 for SynVH-C and 3,000 for SynVH-SD). In parentheses are shown the sequences of the potential loops. The only other potential disulfide loop was a single SynVH-C sequence with Cys residues in FR2 and FR3. In FR2 and FR4, all instances of non-canonical Cys were cases of Trp → Cys changes, which can occur by a single nucleotide substitution. No instances of more than two non-canonical cysteines were observed.