Location of the binding site of the mannose-specific lectin comitin on F-actin.
We have used electron microscopy and computer image processing to produce a three-dimensional reconstruction of F-actin filaments decorated with the putative lectin and actin-binding protein comitin. These reconstructions show that comitin binds to F-actin at high radius primarily to actin subdomain 1. This location is distinctly different from the binding site on F-actin for other actin bundling proteins, such as members of the alpha-actinin family, and may result from the positively charged comitin interacting with negatively charged sites near the actin N terminus in subdomain 1. The location of the comitin binding site and its restriction to subdomain 1 on a single actin monomer is consistent with comitin's having a function distinct from other actin-binding proteins and, for example, would enable comitin to link bundled actin filaments to the Golgi.
Fulgenzi
G
G
Department of Experimental Pathology, University of Ancona, Via Ranieri, Ancona, 60131, Italy.
Graciotti
L
L
Granata
A L
AL
Corsi
A
A
Fucini
P
P
Noegel
A A
AA
Kent
H M
HM
Stewart
M
M
D000199:Actins / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins; D003599:Cytoskeleton / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D037102:Lectins / Q000737:chemistry / Q000378:metabolism*; D008358:Mannose / Q000378:metabolism*; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D008854:Microscopy, Electron; D008958:Models, Molecular; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism*
D000199:Actins; D002352:Carrier Proteins; C034037:F-actin-binding proteins; D037102:Lectins; D008840:Microfilament Proteins; D015800:Protozoan Proteins; D008358:Mannose