Sandbox 122
From Proteopedia
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==='''Background Information'''=== | ==='''Background Information'''=== | ||
[[Image:KapB2_NPC_Schematic.jpg|thumb|alt= Alt text| Figure 1. KapB2 with NLS and cargo moving through the NPC |425px]] | [[Image:KapB2_NPC_Schematic.jpg|thumb|alt= Alt text| Figure 1. KapB2 with NLS and cargo moving through the NPC |425px]] | ||
| - | In eukaryotes, proteins must be transported in and out of the nucleus. This nucleocytoplasmic transport of proteins across the nuclear envelope must occur through the gateway of the NPC. The NPC is a large structure consisting of 456 constituent binding proteins called nucleoporins (Nups).1 Movement through the NPC is facilitated transport that relies on interaction with specific Nups. Importins and exportins are proteins that aid this facilitated transport by both binding to a specific cargo to be transported and interacting with specific Nups located in the central channel of the NPC.2 | ||
| - | Karyopherinβ is a group of proteins that is composed of both importins and exportins. Importins are proteins that carry cargos into the nucleus while exportins serve the opposite function. As of today, twenty different Kapβs have been identified. Each of these Kapβs is capable of recognizing and transporting a specific group of cargos. In order to bind to its cargo a Kapβ has to recognize a Nuclear Localizaton or Export Signal (NLS or NES) is located in the polypeptide chain of the cargo. These signals can vary from 7 amino acids to longer than 100 amino acids in length. | ||
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| - | An importin, such as Kapβ2, binds to a specific cargo by recognition of an NLS and carries the cargo through the NPC by interacting with intrinsically disordered Nups called FG-Nups. FG-Nups line the passageway of the NPC and contain repeats of phenylalanine and glycine. These unstructured FG-Nups form a low-density cloud within the central channel extending from the cytoplasm to the nucleoplasm. The cloud acts as an effective exclusion filter for those particles that do not contain FG repeat binding sites. This is referred to as the zone of selectivity. | ||
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==='''How does Kapβ2 identify its cargo?'''=== | ==='''How does Kapβ2 identify its cargo?'''=== | ||
<StructureSection load='2H4M' size=450 side=right scene='2H4M'/Com_view/1'> | <StructureSection load='2H4M' size=450 side=right scene='2H4M'/Com_view/1'> | ||
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| + | In eukaryotes, proteins must be transported in and out of the nucleus. This nucleocytoplasmic transport of proteins across the nuclear envelope must occur through the gateway of the NPC. The NPC is a large structure consisting of 456 constituent binding proteins called nucleoporins (Nups).1 Movement through the NPC is facilitated transport that relies on interaction with specific Nups. Importins and exportins are proteins that aid this facilitated transport by both binding to a specific cargo to be transported and interacting with specific Nups located in the central channel of the NPC.2 | ||
| + | |||
| + | Karyopherinβ is a group of proteins that is composed of both importins and exportins. Importins are proteins that carry cargos into the nucleus while exportins serve the opposite function. As of today, twenty different Kapβs have been identified. Each of these Kapβs is capable of recognizing and transporting a specific group of cargos. In order to bind to its cargo a Kapβ has to recognize a Nuclear Localizaton or Export Signal (NLS or NES) is located in the polypeptide chain of the cargo. These signals can vary from 7 amino acids to longer than 100 amino acids in length. | ||
| + | |||
| + | An importin, such as Kapβ2, binds to a specific cargo by recognition of an NLS and carries the cargo through the NPC by interacting with intrinsically disordered Nups called FG-Nups. FG-Nups line the passageway of the NPC and contain repeats of phenylalanine and glycine. These unstructured FG-Nups form a low-density cloud within the central channel extending from the cytoplasm to the nucleoplasm. The cloud acts as an effective exclusion filter for those particles that do not contain FG repeat binding sites. This is referred to as the zone of selectivity. | ||
Revision as of 17:51, 29 July 2013
Contents |
3-Dimensional Model of Karyopherin-β2
Students: Mary Acheampong, Rosieva Ashong-Katai, Kavita Bhikhi, Daviana Dueño, Bobby Glover, Lachoy Harris, Alafia Henry, Randol Mata, Hillary Ramirez and Marisa VanBrakle, Hostos-Lincoln Academy.
Introduction
Karyopherin beta 2 (Kapβ2) is an importin that transports various cargo proteins into the nucleus through interactions with nucleoporins, which are proteins of the nuclear pore complex (NPC). One might overlook the significance of this protein but it actually plays a crucial role in the human body by mediating transport of RNA-binding proteins involved in transcription, RNA processing, RNA transport and translation. The structure of Kapβ2 is composed of 20 antiparallel helices called HEAT repeats. These HEAT repeats contribute to Kapβ2’s large superhelical shape. The protein is shown to form two arches: one at the N-terminal and the other at the C-terminal. Through recognition of a nuclear localization signal (NLS) located on its cargo, Kapβ2 binds to its cargo via its C-terminal arch. Release of the cargo is mediated by RanGTP, which once bound, modifies the shape of Kapβ2. This slight conformational change results in the dissociation of the cargo from its binding site.
Background Information
How does Kapβ2 identify its cargo?
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