BioMed Research International

Review Article

The Sarcomeric M-Region: A Molecular Command Center for Diverse Cellular Processes

Table 1

Properties of M-region proteins.


Protein		Localization	Muscle specificity	Residency	PDB ID

M-band organization
Complex 1	Obscurins (ABD)	Periphery	Cardiac/skeletal	Permanent	NA
	Ankyrin-B (Exon 43′)	Periphery	Cardiac	Permanent	NA
	PP2A (B56α)	Periphery	Cardiac/skeletal	Permanent	NA

Complex 2	Titin (Mis4)	Periphery/interior	Cardiac/skeletal	Permanent	NA
	Bin-1	Interior	Cardiac/skeletal (developmental)	Transient	1MV3
	Cdc2 Kinase	Interior	Cardiac/skeletal (developmental)	Transient	NA

	Myomesin	Periphery/interior	Cardiac/skeletal	Permanent	3RBS, 2Y23, 2R15, 2Y25
	SmyD1	Periphery	Cardiac/fast skeletal	Permanent	3N71
	FHLs	Periphery	Cardiac/skeletal	Permanent	2EGQ, 2D8Z

Cytoskeletal remodeling
Obscurins (RhoGEF)		Periphery	Cardiac/skeletal	Permanent	NA
RhoA		Periphery	Cardiac/skeletal	Transient	1LB1, 3KZ1
CRIK		Periphery	Cardiac/skeletal	Transient	NA
Active ROCK1		Periphery	Cardiac/skeletal	Transient	2ETR

Mechanosensing
Titin (Titin Kinase)		Periphery/interior	Cardiac/skeletal	Permanent	4JNW, 1TKI
NBR1		Periphery	Cardiac/skeletal	Permanent	4OLE
P62		Periphery	Cardiac/skeletal	Permanent	2KTR, 3B0F, 2MGW
MuRFs		Periphery	Cardiac/skeletal	Permanent	4M3L, 3Q1D

Metabolism
PFK		Periphery	Cardiac/skeletal	Permanent	4OMT
M-CK		Periphery	Cardiac/skeletal	Permanent	1I0E
AK		Periphery	Cardiac/skeletal	Permanent	2C95
Enolases		Periphery	Cardiac/skeletal	Permanent	3B97, 2XSX
AMPD		Periphery	Cardiac/skeletal	Permanent	2Y2C

Proteasomal degradation
MuRFs		Periphery	Cardiac/skeletal	Permanent	4M3L, 3Q1D

Note: protein domains mediating complex formation or participating in cellular processes are shown in parenthesis when known. Acronyms of proteins are described in the text; ABD: ankyrin binding domain; NA: not available. The PDB files of proteins in Complex 1 and Complex 2, as well as obscurins (RhoGEF) and titin (titin kinase), are associated with the specific domains that mediate binding within the complex; in all other cases, the available PDB files for the entire protein are provided.