A Comparative Study of Rat and Human Tmp21 (p23) Reveals the Pseudogene-Like Features of Human Tmp21-I1

Abstract

Tmp21 (p23) is involved in biosynthetic transport from the endoplasmic reticulum to the Golgi complex. We have recently characterized two cDNA-var-iants of human Tmp21, the Tmp21-isoforms-I and -11. Because of the lack of cDNA sequence data and protein expression data, it was not clear if Tmp21-II encodes a functional Tmp21-protein. Here we describe the cloning of the full length human Tmp21-II transcript. The putative open reading frame of Tmp21-II contains a reading frame jump and a nonsense mutation in comparison to all other Tmp21-I (p23) members. Our data indicate that hum-Tmp21-II is transcribed, but not translated. We conclude that Tmp21-II cDNA derives from a neutral pseudogene, which originates from a duplication event of the human Tmp21-isoform-I.

Key Words:

• protein family
• p24—proteins
• pseudogene