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Structural and nucleotide‐binding properties of YajQ and YnaF, two Escherichia coli proteins of unknown function
Author(s) -
Saveanu Cosmin,
Miron Simona,
Borza Tudor,
Craescu Constantin T.,
Labesse Gilles,
Gagyi Cristina,
Popescu Aurel,
Schaeffer Francis,
Namane Abdelkader,
LaurentWinter Christine,
Bârzu Octavian,
Gilles AnneMarie
Publication year - 2002
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.0217502
Subject(s) - structural genomics , methanococcus , isothermal titration calorimetry , hyperthermophile , biochemistry , escherichia coli , protein structure , biology , structural biology , chemistry , binding site , hypothetical protein , computational biology , gene , archaea
Abstract Structural genomics is a new approach in functional assignment of proteins identified via whole‐genome sequencing programs. Its rationale is that nonhomologous proteins performing similar or related biological functions might have similar tertiary structure. We used dye pseudoaffinity chromatography, two‐dimensional gel electrophoresis, and mass spectrometry to identify two novel Escherichia coli nucleotide‐binding proteins, YnaF and YajQ. YnaF exhibited significant sequence identity with MJ0577, an ATP‐binding protein from a hyperthermophile ( Methanococcus jannaschii ), and with UspA, a protein from Haemophilus influenzae that belongs to the Universal Stress Protein family. YnaF conserves the ATP‐binding site and the dimeric structure observed in the crystal of MJ0577. The protein YajQ, present in many bacterial genomes, is missing in eukaryotes. In the absence of significant similarities of YajQ to any solved structure, we determined its structural and ligand‐binding properties by NMR and isothermal titration calorimetry. We demonstrate that YajQ is composed of two domains, each centered on a β‐sheet, that are connected by two helical segments. NMR studies, corroborated with local sequence conservation among YajQ homologs in various bacteria, indicate that one of the β‐sheets is mostly involved in biological activity.