Table 1.

Biochemical and structural differences in ECC between slow and fast-twitch mammalian fibre types

Proteins	Slow-twitch fibres		Fast-twitch fibres		References
	Isoform	Content/kinetics	Isoform	Content/ kinetics
DHPR	α-1S	+	α-1S	+++	Hollingworth and Marshall 1981; Lamb and Walsh 1987; Franzini-Armstrong et al. 1988.
RyR	RyR1	+	RyR1	+++	Franzini-Armstrong et al. 1988; Appelt et al. 1989; Damiani and Margreth 1994.
PV	α-PV	– to +	α-PV	++ to ++++	Heizmann et al. 1982; Leberer and Pette 1986; Schmitt and Pette 1991; Füchtbauer et al. 1991.
SERCA	SERCA2a	+	SERCA1a	+ to ++	Leberer and Pette 1986; Dulhunty et al. 1987; Ferguson and Franzini-Armstrong 1988; Periamasy and Kalyanasundaram 2007.
Phospholamban	Phospholamban	+	Phospholamban	–	Jorgensen and Jones 1986.
Sarcolipin	Sarcolipin	+	Sarcolipin	+++	Odermatt et al. 1998.
Calsequestrin	CSQ*fast and CSQ*cardiac	+	CSQ*fast	+	Leberer and Pette 1986; Damiani and Margreth 1994.
SRP-27	SRP-27	+	SRP-27	+++	Bleunven et al. 2008
NCX	NCX1	++	NCX1 and 3	+	Fraysse et al. 2001; Hudecova et al. 2004
TnC, TnI, TnT	TnC slow TnI slow TnT slow	+	TnC fast TnI fast TnT fast	++	Bottinelli and Reggiani 2000.
mATPase	Type I	+	Types IIA, IIX/D and IIB	++ to +++	Dubowitz and Pearse 1960; Brooke and Kaiser 1970; Bär and Pette 1988; Schiaffino et al. 1989; Bottinelli and Reggiani 2000.

DHPR dihydropyridine receptors; RyR ryanodine receptors; PV parvalbumin; SERCA sarcoendoplasmic reticulum Ca²⁺ ATPase; CSQ calsequestrin; SRP-27 sarcoplasmic reticulum protein-27 kDa; NCX Na⁺/Ca²⁺ exchanger; TnC troponin C; TnI troponin I; TnT troponin T; mATPase myofibrillar A-band adenosine triphosphatase

– indicates absence of the protein; ++ indicates approximately twofold; +++ between twofold and tenfold; ++++ more than tenfold, in all cases compared to a reference of +