The Sema domain is a

structural domain In molecular biology, a protein domain is a region of a protein's polypeptide chain that is self-stabilizing and that folds independently from the rest. Each domain forms a compact folded three-dimensional structure. Many proteins consist of s ...

semaphorin Semaphorins are a class of secreted and membrane proteins that were originally identified as axonal growth cone guidance molecules. They primarily act as short-range inhibitory signals and signal through multimeric receptor complexes. Semaphorins ...

s, which are a large

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

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

axon guidance Axon guidance (also called axon pathfinding) is a subfield of neural development concerning the process by which neurons send out axons to reach their correct targets. Axons often follow very precise paths in the nervous system, and how they mana ...

. Sema domains also occur in the hepatocyte growth factor receptor (Uniprot: ), Plexin-A3 (Uniprot: ) 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 cells, also known as B lymphocytes, are a type of white blood cell of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted or ...

expression of

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 ...

. 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.

Human proteins containing this domain

MET;

MST1R Macrophage-stimulating protein receptor is a protein that in humans is encoded by the ''MST1R'' gene. MST1R is also known as RON (Recepteur d'Origine Nantais) kinase, named after the French city in which it was discovered. It is related to the c-ME ...

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PLXNA1 Plexin-A1 is a protein that in humans is encoded by the ''PLXNA1'' gene. Interactions Plexin A1 has been shown to interact with AKT1 RAC(Rho family)-alpha serine/threonine-protein kinase is an enzyme that in humans is encoded by the ''AKT1'' ...

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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 effe ...

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PLXNA3 Plexin-A3 is a protein that in humans is encoded by the ''PLXNA3'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ...

; PLXNA4;

PLXNB1 Plexin B1 is a protein of the plexin family that in humans is encoded by the ''PLXNB1'' gene. Function Within neural tissues, the plexin family serves as transmembrane receptors for Semaphorins. Outside of neural tissues, Plexin B1 is implic ...

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PLXNB2 Plexin-B2 is a protein that in humans is encoded by the ''PLXNB2'' gene. Function Members of the B class of plexins, such as PLXNB2 are transmembrane receptors that participate in axon guidance and cell migration in response to semaphorins (Per ...

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PLXNB3 Plexin-B3 is a protein that in humans is encoded by the ''PLXNB3'' gene. Interactions PLXNB3 has been shown to interact with ARHGEF11. Model organisms Model organisms have been used in the study of PLXNB3 function. A conditional knockout m ...

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PLXND1 Plexin-D1 is a protein that in humans is encoded by the ''PLXND1'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ' ...

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SEMA3A Semaphorin-3A is a protein that in humans is encoded by the ''SEMA3A'' gene. Function The ''SEMA3A'' gene is a member of the semaphorin family and encodes a protein with an Ig-like C2-type (immunoglobulin-like) domain, a PSI domain and a Sem ...

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SEMA3B Semaphorin-3B is a protein that in humans is encoded by the ''SEMA3B'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' ...

; SEMA3C; SEMA3D; SEMA3E;

SEMA3F Semaphorin-3F is a protein that in humans is encoded by the ''SEMA3F'' gene. The semaphorin Semaphorins are a class of secreted and membrane proteins that were originally identified as axonal growth cone guidance molecules. They primarily act as ...

; SEMA3G; SEMA4A;

SEMA4B Semaphorin-4B is a protein that in humans is encoded by the ''SEMA4B'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' ...

;

SEMA4C Semaphorin-4C is a protein that in humans is encoded by the ''SEMA4C'' gene. Interactions SEMA4C has been shown to interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit org ...

;

SEMA4D Semaphorin-4D (SEMA4D) also known as Cluster of Differentiation 100 (CD100), is a protein of the semaphorin family that in humans is encoded by the ''SEMA4D'' gene. Function Semaphorin 4D (Sema 4D) is an axon guidance molecule which is secrete ...

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SEMA4F Semaphorin-4F is a protein that in humans is encoded by the ''SEMA4F'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' ...

;

SEMA4G Semaphorin-4G is a protein that in humans is encoded by the ''SEMA4G'' gene. Semaphorins are a large family of conserved secreted and membrane associated proteins which possess a semaphoring (Sema) domain and a PSI domain (found in plexins, sem ...

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SEMA5A Semaphorin-5A is a protein that in humans is encoded by the ''SEMA5A'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth' ...

; SEMA5B; SEMA6A; SEMA6B;

SEMA6C Semaphorin-6C is a protein that in humans is encoded by the ''SEMA6C'' gene. This gene product is a member of the semaphoring family of proteins. Semaphorins represent important molecular signals controlling multiple aspects of the cellular respo ...

; SEMA6D;

SEMA7A Semaphorin 7A, GPI membrane anchor (John Milton Hagen blood group) (SEMA7A) also known as CD108 (Cluster of Differentiation 108), is a human gene. SEMA7A is a membrane-bound semaphorin that associates with cell surfaces via a glycosylphosphatidyl ...

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References

{{InterPro content, IPR001627 Protein domains Protein families Single-pass transmembrane proteins