Table 2.

Structural Attributes and Significant Sites of the bHLH Domain.

Site	Structural	CS	DT	SM	pah	pss	ms	cc	ec	all
1	DP		√	√				C
2	DP	√					C			C
3
4			√	√
5	DP	√			C					C
6	P			√	SC	S	C	C	SC	SC
7			√	√
8	DP	*	√	√		SC	SC		C	SC
9	DP	√						C	C	C
10	P	*			C		C	SC	S	C
11	P	*	√		S		SC			C
12	DP	*	√	√	SC	SC	SC	SC	SC	SC
13	DP	√			C	C	C		C	C
14										S
15	P		√	√					SC	SC
16	B	√		√			C		C	C
17	P	*					C	C	C	C
18
19			√	√	S					S
20	B	*	√	√	C	C	C		C	C
21
22
23	B	√			C	C	C		C	C
24										S
25
26		*
27	B	√								C
28	B	√
50	DPB	√	√	√	C	SC	SC	C	SC	SC
51							S	SC	C	C
52
53	B	√		√					C	C
54	B	√				C			SC	C
55
56
57		*
58
59
60		√
61	B	√
62
63
64	B	√

Note.—The molecular architecture of bHLH positions is compiled from previous work on crystalline structures of animal proteins. Structural attributes noted are DNA contact of the E-box (D), phosphate backbone contact (P), or buried site within the hydrophobic core of the dimerized helices (B). Highly (√) and moderately (*) conserved sites are denoted (CS). Sites integral in the decision tree analysis (DT) and the simplified model (SM) are also reported. Last, SWDA (S) and CVA (C) significant sites are shown within each factor score data set (pah, pss, ms, cc, ec, and all).