RT Journal Article
SR Electronic
T1 On the Emergence of P-Loop NTPase and Rossmann Enzymes from a Beta-Alpha-Beta Ancestral Fragment
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.07.15.204123
DO 10.1101/2020.07.15.204123
A1 Liam M. Longo
A1 Jagoda Jabłońska
A1 Pratik Vyas
A1 Manil Kanade
A1 Rachel Kolodny
A1 Nir Ben-Tal
A1 Dan S. Tawfik
YR 2020
UL http://biorxiv.org/content/early/2020/10/20/2020.07.15.204123.abstract
AB Dating back to the last universal common ancestor (LUCA), the P-loop NTPases and Rossmanns now comprise the most ubiquitous and diverse enzyme lineages. Intriguing similarities in their overall architecture and phosphate binding motifs suggest common ancestry; however, due to a lack of sequence identity and some fundamental structural differences, these families are considered independent emergences. To address this longstanding dichotomy, we systematically searched for ‘bridge proteins’ with structure and sequence elements shared by both lineages. We detected homologous segments that span the first βαβ segment of both lineages and include two key functional motifs: (i) a phosphate binding loop – the ‘Walker A’ motif of P-loop NTPases or the Rossmann equivalent, both residing at the N-terminus of α1; and (ii) an Asp at the tip of β2. The latter comprises the ‘Walker B’ aspartate that chelates the catalytic metal in P-loop NTPases, or the canonical Rossmann β2-Asp that binds the cofactor’s ribose moiety. Tubulin, a Rossmann GTPase, demonstrates the potential of the β2-Asp to take either one of these two roles. We conclude that common P-loops/Rossmann ancestry is plausible, although convergence cannot be completely ruled out. Regardless, both lineages most likely emerged from a polypeptide comprising a βαβ segment carrying the above two functional motifs, a segment that comprises the core of both enzyme families to this very day.Competing Interest StatementThe authors have declared no competing interest.