I don't know what you mean by 'cDNA value'. That could mean any number of things, I suppose, particularly if you don't know what cDNA is (probably not really a thing in this context - cDNA stands for 'complementary DNA', and is what you get when you use reverse transcriptase to generate DNA from RNA).
In addition, CPB2 might be a protein symbol, or it might be an HGNC gene symbol. In this case it's both.
> library(org.Hs.eg.db)
## map CPB2 to NCBI ID
> select(org.Hs.eg.db, "CPB2", c("ENTREZID","SYMBOL"), "ALIAS")
'select()' returned 1:1 mapping
between keys and columns
ALIAS ENTREZID SYMBOL
1 CPB2 1361 CPB2
## add Ensembl
> select(org.Hs.eg.db, "CPB2", c("ENTREZID","SYMBOL","ENSEMBL"), "ALIAS")
'select()' returned 1:1 mapping between keys and columns
ALIAS ENTREZID SYMBOL ENSEMBL
1 CPB2 1361 CPB2 ENSG00000080618
Here I assume it's an HGNC gene symbol. But I don't believe that HGNC gene symbols and protein symbols (like from UniProt) are necessarily the same, so you could also use UniProt to map.
> library(UniProt.ws)
> ws <- UniProt.ws()
> z <- select(ws, "CPB2", c("gene_names","xref_geneid","xref_ensembl","organism_name"), "Gene_Name")
## check that we can get a tractable number of rows
> dim(subset(z, Organism == "Homo sapiens (Human)"))
[1] 4 6
## looks OK
> subset(z, Organism == "Homo sapiens (Human)")
From Entry Gene.Names GeneID Ensembl Organism
2 CPB2 Q96IY4 CPB2 1361; ENST00000181383.10 [Q96IY4-1]; Homo sapiens (Human)
6 CPB2 A0A087WSY5 CPB2 1361; ENST00000439329.5; Homo sapiens (Human)
161 CPB2 A0A6Q8PG06 CPB2 <NA> ENST00000675730.1; Homo sapiens (Human)
162 CPB2 A0A6Q8PHS9 CPB2 <NA> ENST00000674625.1; Homo sapiens (Human)
It does look like CBP2 is an HGNC symbol, not a protein ID though.
Apparently the protein ID is CBPB2.
Thank you, this works well. As for CDNA, I figured out what I need to find, and have made a new post regarding it.