The Sema domain is a structural domain of semaphorin

Semaphorin

Semaphorins are a class of secreted and membrane proteins that act as axonal growth cone guidance molecules. They primarily act as short-range inhibitory signals and signal through multimeric receptor complexes. They are usually cues to deflect axons from inappropriate regions, especially...

s, which are a large family

Protein family

A protein family is a group of evolutionarily-related proteins, and is often nearly synonymous with gene family. The term protein family should not be confused with family as it is used in taxonomy....

 of secreted and transmembrane proteins, some of which function as repellent signals during axon guidance

Axon guidance

Axon guidance is a subfield of neural development concerning the process by which neurons send out axons to reach the correct targets...

. Sema domains also occur in the hepatocyte growth factor receptor and and in viral proteins.

CD100 (also called SEMA4D) is associated with PTPase and serine kinase activity. CD100 increases PMA, CD3 and CD2 induced T cell proliferation, increases CD45 induced T cell adhesion, induces B cell homotypic adhesion and down-regulates B cell

B cell

B cells are lymphocytes that play a large role in the humoral immune response . The principal functions of B cells are to make antibodies against antigens, perform the role of antigen-presenting cells and eventually develop into memory B cells after activation by antigen interaction...

 expression of CD23

CD23

CD23, also known as Fc epsilon RII, or FcεRII, is the "low-affinity" receptor for IgE, an antibody isotype involved in allergy and resistance to parasites, and is important in regulation of IgE levels. Unlike many of the antibody receptors, CD23 is a C-type lectin...

.

The Sema domain is characterised by a conserved set of cysteine residues, which form four disulfide bonds to stabilise the structure. The Sema domain fold is a variation of the beta propeller topology, with seven blades radially
arranged around a central axis. Each blade contains a four- stranded (strands A to D) antiparallel beta sheet. The inner strand of each blade (A) lines the channel at the centre of the propeller, with strands B and C of the same repeat radiating outward, and strand D of the next repeat forming the outer edge of the blade. The large size of the Sema domain is not due to a single inserted domain but results from the presence of additional secondary structure elements inserted in most of the blades. The Sema domain uses a 'loop and hook' system to close the circle between the first and the last blades. The blades are constructed sequentially with an N-terminal beta- strand closing the circle by providing the outermost strand (D) of the seventh (C-terminal) blade. The beta-propeller is further stabilized by an extension of the N-terminus, providing an additional, fifth beta-strand on the outer edge of blade 6.

CD molecules are leucocyte antigens on cell surfaces. CD antigens nomenclature is updated at Protein Reviews On The Web (http://mpr.nci.nih.gov/prow/).

Human proteins containing this domain

MET

Met

-In the arts:* Metropolitan Opera in Manhattan, New York* Metropolitan Museum of Art in Manhattan, New York* Various buildings known as the Metropolitan Opera House* The Metropolitan Ensemble Theater in Kansas City, Missouri-In computing and the Internet:...

; MST1R

MST1R

Macrophage-stimulating protein receptor is a protein that in humans is encoded by the MST1R gene.-Further reading:...

; PLXNA1

PLXNA1

Plexin-A1 is a protein that in humans is encoded by the PLXNA1 gene.-Further reading:...

; PLXNA2

PLXNA2

Plexin-A2 is a protein that in humans is coded by the PLXNA2 gene.This gene encodes a member of the plexin-A family of semaphorin co-receptors. Semaphorins are a large family of secreted or membrane-bound proteins that mediate repulsive effects on axon pathfinding during nervous system development...

; PLXNA3

PLXNA3

Plexin-A3 is a protein that in humans is encoded by the PLXNA3 gene.-Further reading:...

; PLXNA4; PLXNB1

PLXNB1

Plexin B1 is a protein of the plexin family that in humans is encoded by the PLXNB1 gene.-Interactions:PLXNB1 has been shown to interact with ARHGEF12, Rnd1 and ARHGEF11.-Further reading:...

; PLXNB2

PLXNB2

Plexin-B2 is a protein that in humans is encoded by the PLXNB2 gene.-Interactions:PLXNB2 has been shown to interact with ARHGEF11.-Further reading:...

;
PLXNB3

PLXNB3

Plexin-B3 is a protein that in humans is encoded by the PLXNB3 gene.-Interactions:PLXNB3 has been shown to interact with ARHGEF11.-Further reading:...

; PLXND1

PLXND1

Plexin-D1 is a protein that in humans is encoded by the PLXND1 gene.-Further reading:...

; SEMA3A

SEMA3A

Semaphorin-3A is a protein that in humans is encoded by the SEMA3A gene.This gene is a member of the semaphorin family and encodes a protein with an Ig-like C2-type domain, a PSI domain and a Sema domain...

; SEMA3B

SEMA3B

Semaphorin-3B is a protein that in humans is encoded by the SEMA3B gene.-Further reading:...

; SEMA3C

SEMA3C

Semaphorin-3C is a protein that in humans is encoded by the SEMA3C gene.-Further reading:...

; SEMA3D; SEMA3E; SEMA3F

SEMA3F

Semaphorin-3F is a protein that in humans is encoded by the SEMA3F gene.-Further reading:...

;
SEMA3G; SEMA4A

SEMA4A

Semaphorin-4A is a protein that in humans is encoded by the SEMA4A gene.-Further reading:...

; SEMA4B

SEMA4B

Semaphorin-4B is a protein that in humans is encoded by the SEMA4B gene.-Further reading:...

; SEMA4C

SEMA4C

Semaphorin-4C is a protein that in humans is encoded by the SEMA4C gene.-Further reading:...

; SEMA4D

SEMA4D

Semaphorin-4D also known as Cluster of Differentiation 100 , is a protein of the semaphorin family that in humans is encoded by the SEMA4D gene.- Function :...

; SEMA4F

SEMA4F

Semaphorin-4F is a protein that in humans is encoded by the SEMA4F gene.-Further reading:...

; SEMA4G

SEMA4G

Semaphorin-4G is a protein that in humans is encoded by the SEMA4G gene.-Further reading:...

; SEMA5A

SEMA5A

Semaphorin-5A is a protein that in humans is encoded by the SEMA5A gene.Semaphorine 5A also plays a role in autism, reducing the ability of neurons to form connections with other neurons in certain brain regions.-Further reading:...

;
SEMA5B; SEMA6A

SEMA6A

Semaphorin-6A is a protein that in humans is encoded by the SEMA6A gene.In melanocytic cells SEMA6A gene expression may be regulated by MITF.-Further reading:...

; SEMA6B; SEMA6C

SEMA6C

Semaphorin-6C is a protein that in humans is encoded by the SEMA6C gene.-Further reading:...

; SEMA6D; SEMA7A

SEMA7A

Semaphorin 7A, GPI membrane anchor also known as CD108 , is a human gene....

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