Table 1.

Relative abundances of α- and β-carboxysomal proteins in model carboxysomes from Synechococcus elongatus PCC 7942 (β-cyanobacteria), Prochlorococcus marinus MED4 (α-cyanobacteria), and Halothiobacillus neapolitanus C2 (Gammaproteobacteria)^a

Protein category	β-Carboxysomes				α-Carboxysomes
	Protein	S. elongatus PCC 7942 (2% CO2)			Protein	Prochlorococcus MED4		Halothiobacillus C2		Structure
		n	nm	Structure		n	nm	n	nm
Shell proteins	CcmK2-4	6,863	1,143	Hexamer (147)	CsoS1AB	3,232	539	540	90	Hexamer (118)
					CsoS1C	0	0	2,970	495	Hexamer (119)
	CcmO	3,075	1,025b	Trimer (159)	CsoS1D	38	13	? (112, 120)	?	Trimer (120)
	CcmP	?	?	Trimer (161)	CsoS1E	0	0	? (112)	?	Trimer (112)
	CcmL	60	12	Pentamer (123)	CsoS4AB	60	12	60	12	Pentamer (123)
CA enzymes	CcaA	1,058	529	Dimer (173)	CsoSCA	58	29	81	40.5	Dimer (168)
	CcmM-58d
Structural proteins	CcmN	?	?	Monomer? (143)	CsoS2A	0	0	143	329	Monomer?
	CcmM-58	2,177	725	Trimer (98)	CsoS2B	163c	163	186
	CcmM-35	3,829	3,829	Monomer
RubisCO enzyme	RbcL	8,960	1,120	L8S4CcmM-354 (96)	CbbL	1,216	152	2,160	270	L8S8e
	RbcS	6,073			CbbS	1,216		2,160

^aThe protein interactions, sizes, and putative structures of carboxysomes are illustrated in Fig. 7 and 8. Data for S. elongatus PCC 7942 are from references 96 and 159, those for P. marinus MED4 are from reference 112, and those for H. neapolitanus C2 are from reference 66. Other references for data are indicated in parentheses. n, gross number of proteins per carboxysome; n_m, number of protein multimers per carboxysome.

^bCalculated as the difference between the total number of hexagonal units required to cover beta-Cbx (2,168) (96) and the apparent number of CcmKx hexamers (1,143) (159).

^cCsoS2 from MED4 is presumed to be equivalent to the unglycosylated form of CsoS2B from H. neapolitanus (112).

^dCcmM is an active γ-CA enzyme in T. elongatus BP-1, and probably also in other species (138).

^eFrom the crystal structure deposited in the Protein Data Bank (PDB entry 1SVD).