Table 1. Functional analysis of 64 Gap1 mutants.
| Mutated Gap1 region | gap1 allele | Mutated sequence | Mutant class | Amino acid utilization | Intoxication by D-His | Localization |
| gap1-105 | 2-SNT-4 | F | + | + | pm | |
| gap1-101 | 5-SSY-7 | F | + | + | pm | |
| gap1-106 | 8-EKNN-11 | F | + | + | pm | |
| gap1-107 | 12-PDNL-15 | F | + | + | pm | |
| gap1-108 | 16-KHNG-19 | F | + | + | pm | |
| gap1-109 | 20-ITID-23 | F | + | + | pm | |
| gap1-110 | 24-SEFL-27 | F | + | + | pm | |
| gap1-111 | 28-TQEP-31 | F | + | + | pm | |
| gap1-112 | 32-ITIP-35 | F | + | + | pm | |
| gap1-113 | 36-SNGS-39 | F | + | + | pm | |
| N-terminal | gap1-114 | 40-AVSI-43 | F | + | + | pm |
| tail | gap1-115 | 44-DETG-47 | F | + | + | pm |
| gap1-116 | 48-SGSK-51 | F | + | + | pm | |
| gap1-117 | 52-WQDF55 | F | + | + | pm | |
| gap1-118 | 56-KDSF59 | F | + | + | pm | |
| gap1-119 | 60-KRVK-63 | F | + | + | pm | |
| gap1-120 | 64-PIEV-67 | F | + | + | pm | |
| gap1-121 | 68-DPNL-71 | F | + | + | pm | |
| gap1-122 | 72-SEAE-75 | F | + | + | pm | |
| gap1-123 | 76-KVAI-79 | F | + | + | pm | |
| gap1-124 | 80-ITAQ-83 | F | + | + | pm+v | |
| gap1-125 | 84-TPLK-87 | NF | − | − | pm | |
| gap1-126 | 88-HHLK-91 | NF | − | − | pm | |
| gap1-127 | 92-NRH-94 | NF | − | − | pm | |
| gap1-140 | 143-GELA-146 | NF | − | − | ER | |
| gap1-141 | 147-VIFP-150 | PF | + | − | ER+pm | |
| gap1-142 | 151-ISGG-154 | NF | − | − | pm | |
| Loop 2 | gap1-143 | 155-FTTY-158 | NF | − | − | ER |
| gap1-144 | 159-ATRF-162 | NF | − | − | ER | |
| gap1-145 | 163-IDE-165 | NF | − | − | ER | |
| gap1-166 | 166-SFG-168 | PF | + | − | ER+pm | |
| gap1-167 | 219-NMF-221 | F | + | + | pm+v | |
| Loop 4 | gap1-168 | 222-GVK-224 | PF | + | − | pm |
| gap1-146 | 225-GYGE-228 | NF | − | − | pm | |
| gap1-151 | 307-SESV-310 | NF | − | − | pm | |
| Loop 6 | gap1-152 | 311-EPRK-314 | PF | + | − | pm+v |
| gap1-153 | 315-SVPK-318 | PF | + | − | pm | |
| gap1-157 | 405-AEQR-408 | F | + | + | pm | |
| gap1-158 | 409-FLPE-412 | NF | − | − | ER | |
| Loop 8 | gap1-159 | 413-IFSY-416 | PF | + | − | ER + pm |
| gap1-160 | 417-VDRK-420 | NF | − | − | ER | |
| gap1-169 | 421-GRP-423 | NF | − | − | ER | |
| gap1-170 | 424-LVG-426 | F | + | + | pm | |
| gap1-161 | 473-RFRK-476 | NF | − | − | ER | |
| gap1-162 | 475-ALAA-480 | F | + | + | pm | |
| Loop 10 | gap1-163 | 481-QGRG-484 | NF | − | − | ER |
| gap1-164 | 485-LDEL-488 | F | + | + | pm | |
| gap1-165 | 489-SFK-491 | F | + | + | pm | |
| gap1-171 | 492-SPTG-495 | PF | + | − | ER+pm | |
| gap1-139 | 548-KIYK-551 | NF | − | − | ER | |
| gap1-138 | 552-RNWK-555 | NF | − | − | ER | |
| gap1-137 | 556-LFIP-559 | NF | − | − | ER | |
| gap1-136 | 560-AEKM-563 | F | + | + | pm | |
| gap1-104 | 564-DID-566 | NF | − | − | ER | |
| gap1-103 | T-567 | F | + | + | pm | |
| C-terminal | gap1-135 | 568-GRRE-571 | F | + | + | pm |
| tail | gap1-134 | 572-VDLD-575 | F | + | + | pm |
| gap1-133 | 576-LLKQ-579 | F | + | + | pm | |
| gap1-132 | 580-EIAE-583 | F | + | + | pm | |
| gap1-131 | 584-EKAI-587 | F | + | + | pm | |
| gap1-130 | 588-MATK-591 | F | + | + | pm | |
| gap1-129 | 592-PRWY-595 | F | + | + | pm | |
| gap1-128 | 596-RIWN-599 | F | + | + | pm | |
| gap1-102 | 600-FWC-602 | F | + | + | pm |
Strains gap1Δ ura3 and gap1Δ ssy1Δ ura3 transformed with the centromere-based plasmids carrying the indicated gap1 allele were tested for growth on solid media containing citrulline or phenylalanine, respectively, as sole nitrogen source. The gap1Δ ura3 cells were also tested for growth on a proline medium containing D-histidine. The + and − signs mean that transformed cells are able to utilize citrulline and phenylalanine (column “Amino acid utilization”) or to be intoxified by D-histidine (column “Intoxication by D-His)”). Transformed cells of the gap1Δ ura3 strain were also grown on proline as sole nitrogen source and examined under the fluorescence microscope. The Gap1-GFP proteins were localized at the cell surface (pm, plasma membrane), vacuolar lumen (v), or endoplasmic reticulum (ER), or in several of these cell membranes. Mutant classes: F: functional, NF: non functional; PF: partially functional.