Are most human specific proteins encoded by long non-coding RNA?

By looking for a lack of homologues in a reference database of 27 well-annotated proteomes of primates and 52 well-annotated proteomes of other mammals, 170 putative human-specific proteins were identified. Among them, only 2 are known at the protein level and 23 at the transcript level, according to Uniprot. Though 21 of these 25 proteins are found encoded by an open reading frame of a long non-coding RNA, 60% of them are predicted to be at least 90% globular, with a single structural domain. However, there is a near complete lack of structural knowledge about these proteins, with no tridimensional structure presently available in the Protein Databank and a fair prediction for a single of them in the AlphaFold Protein Structure Database. Moreover, the knowledge about the function of these possibly key proteins remains scarce.