Table 1.

Comparison between the un-, mono- and diphosphorylated tarantula RLC NTE peptides charge, conformation, secondary structure and shape

Head	Phosphorylation level	Net charge	RLC shape according to the 3D-Map9	HCH inter-domain salt bridges	HCH inter-domain folding	Helix P intra-domain salt bridges	Helix P extension	Disorder-to-order transition****
BH	Un-P	0	Compact	R39/E58-E61	Folded	none	None	No
BH*	S45 Mono-P	−2	N/A	R39/E58-E61	Folded	pS45/K37	None	No
FH	Un-P	0	N/A	R39/E58-E61	Folded	none	None	No
FH**	S35 Mono-P	−2	Less compact	none	Disrupted	pS35/R38-R39-R42	Partial	Partial
FH***	S35 & S45 di-P	−4	N/A	none	Disrupted	pS35/R38-R39-R42	Full	Full

^*Only the free head is constitutively monophosphorylated at Ser35.^{10, 11} There is no constitutive Ser35 monophosphorylation in the blocked head.^{10, 11}

^**Only the blocked head can be monophosphorylated at Ser45 as the free head is already constitutively monophosphorylated in Ser35. ^{10, 11}

^***Only the free head can be biphosphorylated as it is constitutively monophosphorylated at Ser35 while the blocked head, which is not constitutively monophosphorylated, cannot be diphosphorylated.^{10, 11}

^****Disorder-to-order is used here describe a coil-to-helix transition as originally proposed by Espinoza-Fonseca et al.^{30, 31}

N/A: 3D-map not available, as thick filaments are disordered when activated.⁵