Actinin is a
microfilament
Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other p ...
protein.
Alpha-actinin-1 is necessary for the attachment of
actin
Actin is a protein family, family of Globular protein, globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in myofibril, muscle fibrils. It is found in essentially all Eukaryote, eukaryotic cel ...
myofilament
Myofilaments are the three protein filaments of myofibrils in muscle cells. The main proteins involved are myosin, actin, and titin. Myosin and actin are the ''contractile proteins'' and titin is an elastic protein. The myofilaments act togethe ...
s to the
Z-lines in
skeletal muscle cells,
and to the
dense bodies in
smooth muscle cells
Smooth muscle is an involuntary non- striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit m ...
.
The functional protein is an anti-parallel
dimer, which cross-links the thin filaments in adjacent
sarcomeres
A sarcomere (Greek σάρξ ''sarx'' "flesh", μέρος ''meros'' "part") is the smallest functional unit of striated muscle tissue. It is the repeating unit between two Z-lines. Skeletal striated muscle, Skeletal muscles are composed of tubular ...
, and therefore coordinates contractions between sarcomeres in the horizontal axis.
The non-sarcomeric alpha-actinins, encoded by ''
ACTN1
Alpha-actinin-1 is a protein that in humans is encoded by the ''ACTN1'' gene.
Function
Alpha actinins belong to the spectrin gene superfamily which represents a diverse group of cytoskeletal proteins, including the alpha and beta spectrins an ...
'' and ''
ACTN4'', are widely expressed. ''
ACTN2
Alpha-actinin-2 is a protein which in humans is encoded by the ''ACTN2'' gene. This gene encodes an alpha-actinin isoform that is expressed in both skeletal and cardiac muscles and functions to anchor myofibrillar actin thin filaments and titin to ...
'' expression is found in both
cardiac
The heart is a muscular organ found in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon di ...
and skeletal muscle, whereas ''
ACTN3'' is limited to the latter. Both ends of the rod-shaped alpha-actinin dimer contain actin-binding domains.
Mutations in ''ACTN4'' can cause the kidney disease
focal segmental glomerulosclerosis
Focal segmental glomerulosclerosis (FSGS) is a histopathologic finding of scarring (sclerosis) of glomeruli and damage to renal podocytes.Rosenberg, Avi Z.; Kopp, Jeffrey B. (2017-03-07). "Focal Segmental Glomerulosclerosis". ''Clinical Journal ...
(FSGS).
See also
*
Actin
Actin is a protein family, family of Globular protein, globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in myofibril, muscle fibrils. It is found in essentially all Eukaryote, eukaryotic cel ...
*
Muscle contraction
Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as ...
References
External links
*
EF-hand-containing proteins
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