An Internal Signal Sequence Directs Intramembrane Proteolysis of a Cellular Immunoglobulin Domain Protein

We have constructed three gene fusions that encode portions of a membrane protein, arginine permease, fused to a reporter domain, the cytoplasmic enzyme histidinol dehydrogenase (HD), located at the C-terminal end. These fusion proteins contain at least one of the internal signal sequences of arginine permease. When the fusion proteins were expressed in Saccharomyces cerevisiae and inserted into the endoplasmic reticulum (ER), two of the fusion proteins placed HD on the luminal side of the ER membrane, but only when a piece of DNA encoding a spacer protein segment was inserted into the fusion joint. The third fusion protein, with or without the spacer included, placed HD on the cytoplasmic side of the membrane. These results suggest that (i) sequences C-terminal to the internal signal sequence can inhibit membrane insertion and (ii) HD requires a preceding spacer segment to be translocated across the ER membrane.

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AMIGO, a transmembrane protein implicated in axon tract development, defines a novel protein family with leucine-rich repeats

The Journal of Cell Biology ◽

10.1083/jcb.200209074 ◽

2003 ◽

Vol 160 (6) ◽

pp. 963-973 ◽

Cited By ~ 91

Author(s):

Juha Kuja-Panula ◽

Marjaana Kiiltomäki ◽

Takashi Yamashiro ◽

Ari Rouhiainen ◽

Heikki Rauvala

Keyword(s):

Hippocampal Neurons ◽

Transmembrane Domain ◽

Signal Sequence ◽

Transmembrane Protein ◽

Protein Family ◽

Type I ◽

Fiber Tracts ◽

Neuronal Tissues ◽

Immunoglobulin Domain ◽

Leucine Rich Repeats

Ordered differential display identified a novel sequence induced in neurons by the neurite-promoting protein amphoterin. We named this gene amphoterin-induced gene and ORF (AMIGO), and also cloned two other novel genes homologous to AMIGO (AMIGO2 and AMIGO3). Together, these three AMIGOs form a novel family of genes coding for type I transmembrane proteins which contain a signal sequence for secretion and a transmembrane domain. The deduced extracellular parts of the AMIGOs contain six leucine-rich repeats (LRRs) flanked by cysteine-rich LRR NH2- and COOH-terminal domains and by one immunoglobulin domain close to the transmembrane region. A substrate-bound form of the recombinant AMIGO ectodomain promoted prominent neurite extension in hippocampal neurons, and in solution, the same AMIGO ectodomain inhibited fasciculation of neurites. A homophilic and heterophilic binding mechanism is shown between the members of the AMIGO family. Our results suggest that the members of the AMIGO protein family are novel cell adhesion molecules among which AMIGO is specifically expressed on fiber tracts of neuronal tissues and participates in their formation.

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A Membrane Protease is Targeted to the Relict Plastid of Toxoplasma via an Internal Signal Sequence

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10.1111/j.1600-0854.2007.00637.x ◽

2007 ◽

Vol 8 (11) ◽

pp. 1543-1553 ◽

Cited By ~ 41

Author(s):

Anuradha Karnataki ◽

Amy E. DeRocher ◽

Isabelle Coppens ◽

Jean E. Feagin ◽

Marilyn Parsons

Keyword(s):

Signal Sequence ◽

Internal Signal

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C-terminal sequences can inhibit the insertion of membrane proteins into the endoplasmic reticulum of Saccharomyces cerevisiae

Molecular and Cellular Biology ◽

10.1128/mcb.12.1.276-282.1992 ◽

1992 ◽

Vol 12 (1) ◽

pp. 276-282

Author(s):

N Green ◽

P Walter

Keyword(s):

Saccharomyces Cerevisiae ◽

Endoplasmic Reticulum ◽

Fusion Proteins ◽

Signal Sequence ◽

Dna Encoding ◽

Luminal Side ◽

Internal Signal ◽

Histidinol Dehydrogenase ◽

Arginine Permease ◽

Er Membrane

We have constructed three gene fusions that encode portions of a membrane protein, arginine permease, fused to a reporter domain, the cytoplasmic enzyme histidinol dehydrogenase (HD), located at the C-terminal end. These fusion proteins contain at least one of the internal signal sequences of arginine permease. When the fusion proteins were expressed in Saccharomyces cerevisiae and inserted into the endoplasmic reticulum (ER), two of the fusion proteins placed HD on the luminal side of the ER membrane, but only when a piece of DNA encoding a spacer protein segment was inserted into the fusion joint. The third fusion protein, with or without the spacer included, placed HD on the cytoplasmic side of the membrane. These results suggest that (i) sequences C-terminal to the internal signal sequence can inhibit membrane insertion and (ii) HD requires a preceding spacer segment to be translocated across the ER membrane.

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