Lamin
501125
214647978
2008-05-24T16:04:31Z
BartekChom
4437479
pl
'''Lamins''' are [[fibrous protein]]s providing structural function and transcriptional regulation in the [[cell nucleus]]. They are also involved in the positioning of nuclear pores.
==A and B types==
In [[metazoan]] cells there are A and B type lamins which differ in their length and [[Isoelectric point|pI]]. Human cells have three differentially regulated [[gene]]s.
* B-type lamins are present in every cell. B type lamins, B1 and B2, are expressed from the [[LMNB1]] and [[LMNB2]] genes on 5q23 and 19q13, respectively.
* A-type lamins are only expressed following [[gastrulation]]. Lamin A and C are the most common A-type lamins and are splice variants of the [[LMNA]] gene found at 1q21.
==Function and structure==
These proteins localize to two regions of the [[cell nucleus|nuclear compartment]], the [[nuclear lamina]] -- a proteinaceous structure layer subjacent to the inner surface of the [[nuclear envelope]] and throughout the nucleoplasm in the nucleoplasmic "veil".
Comparison of the lamins to vertebrate cytoskeletal IFs shows that lamins have an extra 42 residues (six heptads) within coil 1b. The c-terminal tail domain contains a [[nuclear localization signal]] (NLS), an Ig-fold like domain, and in most cases a carboxy-terminal CaaX box that is isoprenylated and carboxymethylated (lamin C does not have a CAAX box). Lamin A is further processed to remove the last 15 amino acids and its farnesylated cysteine.
Lamin A and lamin C form homodimers which associate head to tail.
During mitosis, lamins are phosphorylated by MPF which drives the disassembly of the lamina and the nuclear envelope.
==See also==
* [[intermediate filament]]
* [[nuclear lamina]]
* [[laminopathies]]
==External links==
* {{MeshName|Lamins}}
{{Cytoskeletal Proteins}}
[[Category:Structural proteins]]
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