Geminivirus AL3 coat protein (IPR000657)

Short name: Gemini_AL3

Overlapping homologous superfamilies


Family relationships



Geminiviruses are characterised by a genome of circular single-stranded DNA encapsidated in twinned (geminate) quasi-isometric particles, from which the group derives its name [PMID: 16453696]. Most geminiviruses can be divided into two subgroups on the basis of host range and/or insect vector: i.e. those that infect dicotyledenous plants and are transmitted by the same whitefly species, and those that infect monocotyledenous plants and are transmitted by different leafhopper vectors. The genomes of the whitefly-transmitted African cassava mosaic virus, Tomato golden mosaic virus (TGMV) and Bean golden mosaic virus (BGMV) possess a bipartite genome. By contrast, only a single DNA component has been identified for the leafhopper-transmitted Maize streak virus (MSV) and Wheat dwarf virus (WDV) [PMID: 6526009, PMID: 2829117]. Beet curly top virus (BCTV), and Tobacco yellow dwarf virus belong to a third possible subgroup. Like MSV and WDV, BCTV is transmitted by a specific leafhopper species, yet like the whitefly-transmitted geminiviruses it has a host range confined to dicotyledenous plants.

Sequence comparison of the whitefly-transmitted Squash leaf curl virus (SqLCV) and Tomato yellow leaf curl virus (TYLCV) with the genomic components of TGMV and BGMV reveals a close evolutionary relationship [PMID: 1840676, PMID: 1984668, PMID: 1926771]. Amino acid sequence alignments of Potato yellow mosaic virus (PYMV) proteins with those encoded by other geminiviruses show that PYMV is closely related to geminiviruses isolated from the New World, especially in the putative coat protein gene regions [PMID: 1926771]. Comparison of MSV DNA-encoded proteins with those of other geminiviruses infecting monocotyledonous plants, including Panicum streak virus [PMID: 1588314] and Miscanthus streak virus (MiSV) [PMID: 1919519], reveal high levels of similarity.

Geminiviruses contain three ORFs (designated AL1, AL2, and AL3) that overlap and are specified by multiple polycistronic mRNAs. The AL3 protein comprises approximately 0.05% of the cellular proteins and is present in the soluble and organelle fractions [PMID: 8030214]. AL3 may form oligomers [PMID: 8794317]. Immunoprecipitation of AL3 in a baculovirus expression system extracts expressing both AL1 and AL3 showed that the two proteins also complex with each other. The AL3 protein is involved in viral replication.

GO terms

Biological Process

GO:0016032 viral process

Molecular Function

No terms assigned in this category.

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.