ily (176) with members in various Alpha-and Betabaculoviruses (Table 2 and Table 3).
Ac112/113: ac112/113, unknown function
The ORF ac112 encodes a protein (30.9 kDa, 258 aa) with a zinc finger motif (9). Homologs are present in a few baculovirus genomes and in Fowl pox virus (FPF217) (4). The homologs of ac112 and ac113 are fused into one ORF in RoMNPV and re-sequencing showed that this is also the case in AcMNPV C6 (92). The function of this ORF is unknown.
Ac114: ac114, unknown function
The gene ac114 codes for a protein with a predicted mass of 49.3 kDa (424 aa). Ac114 was detected in the capsid of ODVs (20). The gene is unique for group Ⅰ NPVs and contains a conserved domain belonging to the DUF1098 superfamily of unknown function (176).
Ac 115: pif-3, per os infectivity factor 3
PIF-3 is a 23.0 kDa (204 aa) baculovirus core protein required for oral infectivity of larvae. It has a predicted N-terminal transmembrane domain and is located most likely on the inside of the ODV envelopes (249). PIF-3 does not affect ODV binding or envelope fusion with larval midgut cells, but may play a crucial role further downstream in the infection process (203).
Ac116: ac116, unknown function
The putative gene product encoded by ac116 is 6.4 kDa (58 aa) and homologs are only present in the closely related BmNPV, Plutella xylostella (Plxy) MNPV and RoMNPV (Table 2). The function of the transcribed ac116 gene (287) is unknown.
Ac117: ac117, unknown function
The gene is transcribed (287) and codes for a putative protein with a molecular mass of 11.0 kDa (95 aa). Homologs are present in several other members of the genus Alphabaculovirus (Table 2).The function of ac117 in the viral life cycle is not known.
Ac118: ac118, unknown function
The gene codes for a protein (18.7 kDa, 157 aa) with unknown function and an RNA copy was found (287). A homolog of ac118 is only present in the genomes of the closely related PlxyMNPV and RoMNPV (Table 2).
Ac119: pif-1, per os infectivity factor 1
PIF-1, previously called PIF, is a low-abundant 59.7 kDa (530 aa) baculovirus core protein essential for oral infectivity in insect larvae (249). The Spodoptera exigua (Se)MNPV PIF-1 protein is present in ODVs (128), most likely anchored in the membrane by a conserved N-terminal transmembrane region (249). PIF-1 was not found in a proteomic analysis of AcMNPV ODVs (20), suggesting a low abundance. Together with PIF-2 it mediates binding of ODVs to epithelial midgut cells (203).
Ac120: ac120, unknown function
The putative gene product encoded by ac120 has a molecular mass of 9.5 kDa (82 aa). There is no information about the role of the ac120 product in the baculovirus life cycle. Homologs of ac120 can only be found in genomes of several other members of the genus Alphabaculovirus (Table 2).
Ac121: ac121, unknown function
A homolog of ac121 is only present in the genome of BmNPV (Table 2) and encodes a 6.7 kDa (58 aa) protein. There is evidence that Ac121 stimulates expression of the viral protein 39K (ac36) by up-regulation of IE1 (ac147) expression (78). Ac121 does not influence late gene expression (149).
Ac122: ac122, unknown function
Ac123: pk2, protein kinase 2
The gene pk2 is transcribed early as an 1.2 kb RNA and encodes the protein PK2 (24.9 kDa, 215 aa). PK2 contains six out of eleven motifs conserved among eukaryotic protein kinases (152). Truncation of the pk2 gene has no effect on the number, size, or appearance of viral plaques and on the kinetics of protein synthesis or protein phosphorylation profiles during virus infection in cultured Sf21 cells. PK2 mutants show no difference in infectivity or virulence in larval bioassays, neither in production of OBs as compared to wild type AcMNPV infection (152). PK2 prevents the phosphorylation of the eukaryotic translation initiation factor 2α (eIF2α). This phosphorylation is induced by stress, as caused by viral infection and inhibits protein synthesis in general (39). PK2 is a homolog of cellular eIF2α kinases, but is an inactive, truncated enzyme. By forming hetero-dimers with the cellular eIF2α kinas